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Programming With .NET Introduction

Course 502

502/CN/P.1/403/O.3

© Learning Tree International, Inc. All rights reserved. Not to be reproduced without prior written consent.

© LEARNING TREE INTERNATIONAL, INC.All rights reserved.

All trademarked product and company names are the property of their respective trademark holders.

No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, or translated into any language, without the prior written

permission of the publisher.

Copying software used in this course is prohibited without the express permission of Learning Tree International, Inc. Making unauthorized copies of

such software violates federal copyright law, which includes both civil and criminal penalties.


The author would like to acknowledge the following for their contributions tothis course:

Stacy Diehl

Ulf Malmström

Candice Ciampa

Mike Murray

Nancy Wong Bryan

My wife, Martine

Lysander Rehnstrom

Joey Gagliardo

Acknowledgments

Introduction and Overview


In this course, you will

Design and program applications using Microsoft .NET and Visual Studio

Learn the syntax of the Visual Basic (VB) and C# programming languages

Write a .NET Windows Forms application

Code for reuse using object orientation, inheritance, and class libraries

Create and program an ASP.NET website

Allow users to log in and create accounts using Web Forms authentication

Create a SQL Server database

Save and access database data using .NET

Deploy .NET Windows and web applications

Course Objectives

20-


Introduction and Overview

Chapter 1 Starting to Program .NET With Visual Studio

Chapter 2 C# and Visual Basic Language Syntax

Chapter 3 Programming Windows User Interfaces

Chapter 4 Object-Oriented Programming

Chapter 5 Designing Web User Interfaces With ASP.NET

Chapter 6 Saving Data With Relational Databases

Chapter 7 Deployment

Chapter 8 Course Summary

Course Evaluation

Appendix A Answers to Review Questions and Glossary

Course Contents

30-


Course Materials

Course Notes• Copies of all slides and supplemental

presentation material

Exercise Manual

Visit your My Learning Tree account for additional information and resources related to this course

40-


Can be done in either C# or Visual Basic

Many exercises have bonuses• Have much less direction• Designed to apply what you have learned

C:\502 folder• Contains starting points for each

exercise• Contains incremental solutions

for all exercises• Feel free to copy and paste code

from the finished exercisesolutions if you prefer

Solution launcher provides quickaccess to exercises and solutions

Course Exercises

C# code

VB code

Exercise starting points

Finished exercises

50-


Please visit our .NET blog• http://dotnet.learningtree.com

Learning Tree International’s .NET Blog

60-

Starting to Program .NET With Visual Studio

Chapter 1

2© Learning Tree International, Inc. All rights reserved. Not to be reproduced without prior written consent. 1-

After completing this chapter, you will be able to • Create a simple .NET program

To accomplish this, you will Create a Visual Studio project Learn the basics of .NET programming Design and program classes Add data to classes with properties Add behavior to classes with methods Begin programming our case study

Chapter Objectives


Chapter Contents

Creating Programs in Visual Studio Hands-On Exercise 1.1

Analyzing the Flash Cards Application

Classes, Variables, and Properties

Objects

Hands-On Exercise 1.2

Methods



The .NET Framework is so large, parts of it have been given names• ASP.NET is the part of the framework used for building Web applications• Windows Forms and WPF are used for building desktop applications

.NET Application Types

ASP.NET Windows Forms

ADO.NET

Windows Presentation Foundation (WPF)

LINQ to SQL

Windows Communication Foundation (WCF)

Windows Workflow Foundation (WF)

C# and VB Language Enhancements

LINQ to Objects Entity Framework

System.XML Web Services Remoting

ClickOnce Deployment

2.0

3.0

3.5

Parallel Computing F#, Iron Python, Iron Ruby

4.0

Dynamic Language Runtime

Vers

ions

4.5 Windows Azure HTML 5

Windows 8 and Windows Phone Development


Visual Studio is the main tool for creating .NET applications

Any kind of computer application can be created with .NET• Windows applications• Web applications• Console

applications• And others

Visual Studio


Visual Studio Solutions are used to create applications• Solutions consist of one or more projects

Projects consist of • Source-code files• References to external code libraries used by the project• Resources (like graphics and audio files)• Configuration files

To create a Visual Studio project:• Open Visual Studio• Select File | New |

Project• This opens the New

Project dialog

Visual Studio Solutions and Projects


Select a programming language• Visual Basic and C# are the most common

– These languages will be covered in this course

Specify the name of theproject• Location will be a folder

to save the project in

Choose the project template• Windows, Console,

Empty Project, etc.

New Project Dialog


Choosing a Language Illustrated

MicroSoft Intermediate Language code (MSIL)

Hardware

Operating system

Common Language Runtime (CLR)

VB code

VB compiler (vbc.exe)

C# code

C# compiler (csc.exe)

Other languages

Other language compilers

Machine code


Choosing a template tells Visual Studio to• Set references to .NET libraries that

are most common for that application type• Set default project properties appropriate

to that application type• Create default files that can be used as

templates

In the exercise, you will choose the Empty Project template• This is to demonstrate some of what

Visual Studio automates

Visual Studio Project Templates


Used to manage projects in Visual Studio• Lists a project’s files and references

Right-click the project to• Add code files (classes)• Access project properties• Build the project (compile)• And more

Solution Explorer


A class is the primary container for code in a .NET program• Defined using the Class keyword• Classes contain data (variables) and behavior (functions)

Visual Basic and C# code:

Classes can contain• Properties (to save data)• Methods (functions declared inside a class)• Events (messages sent from the class)• Constructors (functions that are run automatically when the class is used)

Classes

We’ll discuss each of these in detail later

public class FlashCards{

}

Public Class FlashCards

End Class

def·i·ni·tion


All code in .NET must be written inside a class• Classes are kept in source-code files

To create a class1. Right-click the project in Solution Explorer2. Select Add | Class3. Give the class a name

appropriate to the code it will contain

Adding Code


A statement is a line of code

In Visual Basic, statements end at the end of a line• Long lines can be divided using the space + underscore character ( _)

– Since 2010, VB supports implied line continuation, so the underscore is not always necessary

In C#, statements end with a semicolon (;)

Visual Basic code:

Statements

Each line of code is a statement

Space + underscore indicates that multiple lines are treated as a single statement

def·i·ni·tion


C# code:

Statements

Each statement ends with a semicolon

Missing semicolon indicates that multiple lines are treated as a single statement


When a program starts, the computer needs to know what to do first• In .NET, that is a function called Main• The .NET runtime calls this function when the program executes

Visual Basic code:

C# code:

A Program’s Entry Point

Public Class StartupPublic Shared Sub Main()

Console.WriteLine("Welcome to Flash Cards!")Console.ReadLine()

End SubEnd Class

class Startup{

public static void Main(){

Console.WriteLine("Welcome to Flash Cards!");Console.ReadLine();

}}

We’ll discuss creatingfunctions and the Shared/statickeywords later


We’ve been hired by our local elementary school to write a program to help the kids master basic math skills (addition, subtraction, multiplication, and division). Essentially, the program is an electronic version of flash cards, which you may have been quizzed with when you were a child.

To keep costs down, the school has asked us to keep the program as simple as possible, using just a character-based User Interface (UI).

Later, the school is hoping to add more features if the program is well received.

Case Study: The Flash Cards Program

∑Xii=1X =

n

ŋ


Two main methods:• Console.WriteLine()—Outputs a message to the user• Console.ReadLine()—Waits for the <Enter> key and collects the user’s

input• Console application ends when there is nothing left for it to do

– Use Console.ReadLine() to prevent the program from exiting

Programming Console Applications


Chapter Contents

Creating Programs in Visual Studio

Hands-On Exercise 1.1 Analyzing the Flash Cards Application


Objects


Methods




In your Exercise Manual, please refer to Hands-On Exercise 1.1: Creating the FlashCards Project


Helps the programmer find errors• Breakpoints can be set to stop the program’s execution• Can single-step through code by pressing the <F11> key• Can resume the program by pressing <F5>

To set a breakpoint, click the gray border on the left side of the code window

The Debugger


Add comments to code and document what everything does• In VB, anything prefixed with an apostrophe (') is ignored by the compiler• In C#, use two slashes (//)

Make your code easy for the next programmer to understand• Use descriptive variable and method names and avoid abbreviations• Divide long, complex statements into multiple statements• Include detailed messages when throwing exceptions

Commenting Code

Remember, the next programmer who has to figure out your code will probably be you!


Chapter Contents





Objects


Methods



We talked to the customer regarding how the Flash Cards program should work—below is what we found:

The program should ask the students (users) who they are

Before each question, the program should ask students what math operation they want to be quizzed on• Addition, subtraction, multiplication, or division

It will build an equation using two randomly generated numbers between 0 and 99

The students will then provide the answer and be told whether they were correct

The program should keep track of the number of questions the students answer correctly and inform them of their percentage score after each answer

Each time, the students should be asked whether they want to continue

Our Case Study: Flash Cards Requirements


Your instructor will divide you into groups, then take a few minutes to do the following: • The data required by the program will be stored inside properties• Read through the requirements• In the top portion of the box below, list the properties needed by the program

Analyzing the Data Required for Flash Cards

FlashCardsGame

Methods will go here

Do Now


Again in your groups, take a few minutes to do the following: • The things the program will need to do will determine its methods• Again, read through the requirements• Below the properties, list the methods needed in the Flash Cards program

Analyzing Flash Cards Functionality

FlashCardsGame

Properties should be here

Do Now


The properties and the methods (functions) we will use in the Flash Cards program are documented below:

Solution: Flash Cards Requirements

FlashCardsGame

UserOperationNumber1Number2TriesCorrect

GenerateNumbers()BuildEquation()CheckAnswer()CalculatePercentCorrect()CalculateCorrectAnswer()


Chapter Contents




Classes, Variables, and Properties Objects


Methods



A variable is a named location in memory used to store, retrieve, and change data

Must specify two things when declaring a variable:• Variable name• Data type

Variable name rules:• Must begin with a letter or underscore ( _ )• Can contain only letters, numbers, and underscores ( _ )• Cannot be a keyword• In C#, variable names are case-sensitive, but not in Visual Basic

Data type• Specifies how much memory to reserve• The computer ensures that the data at that location is valid

Variables def·i·ni·tion


Visual Basic code:

C# code:

Variable Declaration Examples

string input;double answer;

Dim input As StringDim answer As Double


VB keyword C# keyword TypeString string Used to store characters (text)Integer int Used to store whole numbersDouble double Used to store numbers with a decimalDate DateTime Used to store dates and timeBoolean bool Used to store true or false

Some Common Data Types

We’ll cover data types in detail later


VB and C# Operators

Operation VB C# NotesAddition + +

Subtraction - -

Multiplication * *

Division / /

Integer Division \ N/A In C#, dividing integers results in integer divisionModulus Mod % Divides, and returns only the remainderExponentiation ^ N/A Use Math.Pow() function in C#

Increment N/A ++ Add 1Decrement N/A -- Subtract 1Assignment = =

Add to += += x += 1 is equivalent to x = x + 1

Subtract from -= -= x -= 1 is equivalent to x = x - 1

Multiply by *= *= x *= 1 is equivalent to x = x * 1

String concatenation & or + +


Properties provide access to the data stored in a class• Short syntax allows them to be created with a single line• Longer syntax on next slide allows additional logic to be added to properties

Visual Basic code:

C# code:

Properties def·i·ni·tion

Public Property User As StringPublic Property Number1 As DoublePublic Property Number2 As DoublePublic Property Correct As Integer

public string User{ get; set; }public double Number1{ get; set; }public double Number2{ get; set; }public int Correct{ get; set; }


Logic can be added to properties when they are fully implemented• Allows for data manipulation or validation to be done within the property

Properties contain two parts:• Get clause is used when the value of the property is requested• Set clause is used when a change in the value is requested

Properties could be read- or write-only by removing the Set or Get clause

Data is in this case actually saved in _operation variable• Keyword Private means that _operation cannot be accessed directly

from outside the class

VB code:

Fully Implemented Properties

Private _operation As StringPublic Property Operation() As String

GetReturn _operation

End GetSet(value As String)

_operation = valueEnd Set

End Property


C# code:

Fully Implemented Properties

private string _operation;public string Operation{

get{

return _operation;}set{

_operation = value;}

}


Chapter Contents





Objects Hands-On Exercise 1.2

Methods



An object is an instance of a class in memory• Hence the term object-oriented programming

Create a variable of the class type and construct it with the New keyword• New tells the computer to create an instance of the class in memory

Visual Basic code:

• Declaration can be done on two lines

C# code:

Objects

Dim game As New FlashCardsGame()

Dim game As FlashCardsGamegame = New FlashCardsGame()

def·i·ni·tion

FlashCardsGame game = new FlashCardsGame();

FlashCardsGame game;game = new FlashCardsGame();


Once constructed, an object’s public properties and methods can be accessed

Visual Basic code:

C# code:

Using an Object

User is a property of the FlashCardsGame class

GenerateNumbers is a method of the FlashCardsGame class

game.User = Console.ReadLine();Console.WriteLine("Welcome " + game.User);game.GenerateNumbers();

game.User = Console.ReadLine()Console.WriteLine("Welcome " + game.User)game.GenerateNumbers()

game is an instance of the FlashCardsGame class


Chapter Contents





Objects

Hands-On Exercise 1.2 Methods




In your Exercise Manual, please refer to Hands-On Exercise 1.2: Creating the FlashCardsGame Class


Chapter Contents





Objects


Methods Hands-On Exercise 1.3


A method is a named block of code that performs a series of statements• Must be inside a class• Require a unique name that should be descriptive• May or may not return a value • Can have arguments (parameters) passed to them

Public methods can be called from outside the class

Private methods are used as helper functions• Called only from within the class

Methods def·i·ni·tion


Methods usually return some value• Can be any data type• Return data type is defined when defining the function• Return keyword is used to return the value and exit the function

Visual Basic code:

C# code:

Coding Methods

Public Function BuildEquation() As String

'Code omittedReturn Number1.ToString() + "+" + Number2.ToString()

End Function

public string BuildEquation(){

// Code omittedreturn Number1.ToString() + "+" + Number2.ToString();

}


Often arguments or variables are passed into methods• Allows the function to be more flexible• Each argument must have a name and data type like any other variable• Any number of arguments can be passed, separated by commas


Passing Arguments to Methods

Public Function CheckAnswer(answer As Double) _ As Boolean

'Code omittedIf CalculateCorrectAnswer() = answer Then…

End Function

public bool CheckAnswer(double answer){

// Code omittedif (CalculateCorrectAnswer()== answer)…

}


Some methods just do things and do not return any value• In VB, these are known as subroutines

– Defined with the keyword Sub• In C#, these are functions with a return type of void

Visual Basic code:

C# code:

Methods That Do Not Return Anything

public void GenerateNumbers(){

Random randomNumber = new Random();Number1 = randomNumber.Next(0, 99);Number2 = randomNumber.Next(0, 99);

}

Public Sub GenerateNumbers()Dim randomNumber As New Random()Number1 = randomNumber.Next(0, 99)Number2 = randomNumber.Next(0, 99)

End Sub2


All code (fields, methods, properties, events, and constructors) must be inside a class

VB code

Code Placement

Public Class FlashCardsGame

Public Property User As StringPublic Property Number1 As DoublePublic Property Number2 As Double

Public Sub GenerateNumbers()Number1 = 1Number2 = 2

End Sub

Public Function BuildEquation() As StringReturn "1 + 2"

End Function

End Class

Class starts

Class ends

Properties

Method

Method


C# code

Code Placement

public class FlashCardsGame{

public string User{ get; set; }public double Number1{ get; set; }public double Number2{ get; set; }


Number1 = 1;Number2 = 2;

}

public string BuildEquation(){

return "1 + 2"; }

}

Class starts

Class ends

Properties

Method

Method


Chapter Contents






Objects

Methods




In your Exercise Manual, please refer to Hands-On Exercise 1.3:

Adding Methods to the FlashCardsGame Class


You are now able to• Create a simple .NET program

You have Created a Visual Studio project Learned the basics of .NET programming Designed and programmed classes Added data to classes with properties Added behavior to classes with methods Begun programming our case study

Chapter Summary


What are the different types of applications that can be created with .NET?

What is a .NET program’s entry point?

Which are the two most common .NET languages? Which is better?

What tool in Visual Studio is used to manage projects?

What is a statement?

Chapter 1 Review Questions


Code in .NET must be written inside a:

Name three things that might be in a class:

What must be specified when declaring a variable?

Properties provide access to what within a class?

Define a method:


C# and Visual Basic Language Syntax

Chapter 2


After completing this chapter, you will be able to • Program in C# and Visual Basic

To accomplish this, you will Investigate data types and type conversions Use If and Case statements to allow programs to make decisions Program loops Handle errors

Chapter Objectives


Chapter Contents

Data Types and Type Conversions Hands-On Exercise 2.1

Decision-Making Statements


Repeating Code With Loops


Exceptions



When a variable is declared, its data type is specified• Determines the amount of memory allocated for the variable

.NET ensures that a variable’s value is valid for its type• This is known as type safety

If we enter the following code, what would happen if the user typed Joe?

_____________________________________________________________

A variable must be of an appropriate data type for the data it will contain

Sometimes its value must be converted to other data types

Data Types

Dim Age As IntegerConsole.WriteLine("Enter your age.")Age = Console.ReadLine()


Can contain any series of letters, numbers, and symbols• Can be very large• Amount of memory consumed depends on the size of the string

In .NET, a wealth of functionality is built into the String data type• Below are some common examples:

Strings

Member DescriptionLength Returns the number of characters in the string

ToUpper() Converts the string to all uppercase characters

ToLower() Converts the string to all lowercase characters

Trim() Removes all whitespace characters from the beginning and end of the string

Replace() Replaces all occurrences of one string of characters with anotherStartsWith() Determines whether the string begins with a specified value

SubString() Retrieves part of the string; enter the start character and the number of characters to retrieve; the first character is character 0

IsNullOrEmpty() Returns a true if the string has no value.


What is the value of String2?

Now what is the value of String2?

Now what is the value of String2?

Examples of Using the String Type


Adding strings together is called concatenation• Done with the + operator in both C# and VB• Can also be done with & in VB

Complex concatenation can be simpler with the String.Format()method

• The {#} characters embedded in the string are placeholders for variables

• After the string, the correct number of arguments are passed to the function

• The variables replace the placeholdersin the resulting string

String Concatenation and String.Format()

Console.WriteLine("Welcome " + game.User);

Console.WriteLine( String.Format("Your score is {0} out of {1} for {2}%", game.Correct, game.Tries, game.PercentCorrect));


Are numbers that do not include a decimal• Can be positive or negative

In .NET, there are different types of integers• The more memory the integer consumes, the bigger the number can be• Types include Short, Integer, and Long

When declaring a variable, which integer type should you choose?

Integers


The code example below shows the largest number for each integer type• i consumes 2 bytes of memory• j consumes 4 bytes of memory• k consumes 8 bytes of memory• The values could be similarly negative

• Is it necessary to memorize the upper and lower bound of each type?

In C#, the types are short, int, and long

Integer Sizes


Real Numbers

Numbers that include a decimal• Can be both positive and negative• Range depends on the precision (number of decimal places)

VB type C# type Bytes Used forSingle float 4 Small real numbersDouble double 8 Large real numbersDecimal decimal 16 Currency calculations


Numeric types have a method called Parse()• Expects a string argument• Will do the conversion if it is possible

If the string cannot be successfully converted to the number, an exception is raised

Visual Basic code:

Converting Strings to Numbers

More on exception handling later


TryParse() takes two arguments and returns True or False• First argument is the string to be converted to a number• Second argument is the numeric variable that will hold the conversion

– In C#, the out keyword must be used before second argument• If the string cannot be converted to a number, False is returned; otherwise True


Converting Strings to Numbers With TryParse()

Dim input As StringDim answer As Doubleinput = Console.ReadLine()If Double.TryParse(input, answer) = False Then

Console.WriteLine("Invalid input, try again.")End If

string input;double answer;input = Console.ReadLine();if (Double.TryParse(input, out answer) == false){

Console.WriteLine("Invalid input, try again.");}


All .NET types have a method called ToString()• Always converts that type to a string representation of the value

C# code:

Converting Numbers to Strings


Stored as a number but can be only True or False• ToString() method returns string “True” or “False”• Boolean.Parse() method takes a string “True” or “False” and converts it to

a Boolean


Boolean Data Type


Dates

Represented as DateTime type• Actually stored as an 8-byte numeric variable• Range from 1/1/0001 to 11:59:59 PM 12/31/9999• Time is precise to 100 nanoseconds (ticks)

Numerous methods for performing date and time calculations• DateTime.Now returns the current date and time• Add(), AddDays(), AddHours(), AddMilliseconds(), etc.

Numerous methods for converting dates and time to a string

Method() Returns (on a U.S. computer)ToString() 9/8/2004 7:47:25 PMToLongDateString() Wednesday, September 08, 2004ToShortDateString() 9/8/2004ToLongTimeString() 7:47:25 PMToShortTimeString() 7:47 PM


An array is a variable that can contain multiple values

The size of the array must be specified when declaring it• Each value is referred to by its index number• Indexes in .NET always begin with the number 0

In Visual Basic, when declaring an array, the upper bound is specified• Use parentheses for accessing items in the array

In C#, the number of items that the array can hold is specified• Use square brackets for accessing items in the array

Arrays

Dim MonthSales(11) As Double

double[] MonthSales = new double[12];

def·i·ni·tion


Chapter Contents

Data Types and Type Conversions

Hands-On Exercise 2.1 Decision-Making Statements




Exceptions




In your Exercise Manual, please refer to Hands-On Exercise 2.1: Programming Data Types


In VB and C#, data-type conversions can be done in the following ways:• Use some method built into the data type• Use a method built into the System.Convert class• Use a function built into the language

– More common in Visual Basic• Perform a cast

Type Conversions Review


If there is a method of the data type that will do the conversion, use it• It will likely be the most efficient

VB and C# code:

Type Conversions: Code Examples

Dim s As String = "100"Dim n As Double = 100.0Dim i As Integeri = Integer.Parse(s)i = System.Convert.ToInt32(s)i = CInt(s)i = CType(n, Integer)

string s = "100";double n = 100.00;int i;i = int.Parse(s);i = System.Convert.ToInt32(s);i = (int)n;

We’ll see more examples of doing type casts later in the course


Implicit Type Conversions

.NET will do an implicit type conversion when there cannot be loss of data• Larger types can be assigned values of smaller types implicitly• Floating-point numbers can be assigned integer values implicitly

In the following code sample, which statement is not valid and why?


Chapter Contents



Decision-Making Statements Hands-On Exercise 2.2



Exceptions



Sometimes the program needs to decide only whether to do something• If the divisor does not equal zero, then do the math

Can be written on one line or multiple lines• If written on multiple lines, the block of code needs to be ended

Visual Basic code:

If Statement

In VB, an If block ends with the End Ifstatement

In C#, if blocks are contained inside curly braces

C# code:


If-Then statements can test against one or more criteria expressions• Boolean operators are used to determine whether a variable meets the criteria

Some Visual Basic and C# examples:

Criteria Expressions

If Job = "Programmer" Then GiveRaise()if(LoggedIn != true) Response.Redirect("Login.aspx");If Age < 18 Then ApplyDiscount()if (Hours > 40) CalculateOverTime();If EndDate >= StartDate Then RunReport()

To test for VB C#Equality = ==

Inequality <> !=

Less than < <

Less than or equal to <= <=

Greater than > >

Greater than or equal to >= >=


Sometimes both of two criteria have to be true• Separate the criteria with AndAlso in Visual Basic or && in C#

Sometimes at least one of two criteria has to be true• Separate the criteria with OrElse in Visual Basic or || in C#

Multiple Criteria

If HireDate < Now.AddYears(-3) AndAlso LastRaise < Now.AddYears(-1) ThenPayRate = PayRate * 1.1

End If

If HireDate < Now.AddYears(-3) OrElse LastRaise < Now.AddYears(-1) ThenPayRate = PayRate * 1.1

End If

if (HireDate < DateTime.Now.AddYears(-3) && LastRaise < DateTime.Now.AddYears(-1)){

PayRate = PayRate * 1.1;}

if (HireDate < DateTime.Now.AddYears(-3) || LastRaise < DateTime.Now.AddYears(-1)){

PayRate = PayRate * 1.1;}


Criteria expressions can be as complex as needed• Statements can be grouped together with parentheses

Multiple Criteria

If (HireDate < Now.AddYears(-3) AndAlso LastRaise < Now.AddYears(-1)) _OrElse Job = "Programmer" Then

PayRate = PayRate * 1.1

End If

if ((HireDate < DateTime.Now.AddYears(-3) && LastRaise < DateTime.Now.AddYears(-1))|| Job == "Programmer")

{PayRate = PayRate*1.1;

}


Else clause allows for an alternative branch• If something is true, pursue one path• Else, go a different way


If-Then-Else


Sometimes more than two branches are required• ElseIf clause allows for as many branches as required• Else can be used as the final case

Visual Basic code:

If-Then-ElseIf-Else

Note that only the code inside the first true condition will apply


C# code:

If-Then-ElseIf-Else

Note that only the code inside the first true condition will apply


Is an alternative to an If statement with multiple conditions• A variable is checked against multiple cases • The code in the first matching case executes• Can have a default case at the end

Can be easier to read than a complex If statement

Visual Basic code:

Select…Case (switch) Statement


C# code:

Select…Case (switch) Statement

In C#, each case must end with some flow control statement. This is most often done with a break statement. A returnwould also work.


Chapter Contents




Hands-On Exercise 2.2 Repeating Code With Loops


Exceptions




In your Exercise Manual, please refer to Hands-On Exercise 2.2: Using If Statements


Chapter Contents





Repeating Code With Loops Hands-On Exercise 2.3

Exceptions



Are used when• The number of iterations is known• The number of iterations can be easily calculated

Require a variable to act as a counter, and a beginning and ending range• Each time through the loop, the variable is incremented by the amount

specified

For-Next Loops


Visual Basic code:

C# code:

• What is another example of when a For-Next loop would be appropriate?

For-Next Loops

Public Sub PrintMonthlySales()

For i As Integer = 0 To 11 Step 1Console.WriteLine(Sales(i))

Next

End Sub

public void PrintMonthlySales(){

for (int i = 0; i < 12; i++){

Console.WriteLine(Sales[i]);}

}

In VB, an increment of 1 is the default, so it would rarely be specified. If one wanted to go backward, specify Step -1


Are used when• It is impossible to know how many times to perform the loop• It would be too inefficient to make that calculation

Each statement inside the Do-Loop block is repeated

Visual Basic code:

• What is wrong with the above loop?

Do-While Loops


Use when the operations inside the loop must always happen at least once


Give an example of when a bottom-evaluation Do loop would be appropriate:

Bottom-Evaluation Loops

do{game.GenerateNumbers();// Code to play the Flash Cards game omittedConsole.WriteLine("Do you want to play again (Y or N)?");input = Console.ReadLine();

} while (! input.ToUpper().StartsWith("N"));

Dogame.GenerateNumbers()' Code to play the Flash Cards game omittedConsole.WriteLine("Do you want to play again (Y or N)?")input = Console.ReadLine()

Loop While Not input.ToUpper().StartsWith("N")


Use when the operations inside the loop may never be needed


• Give an example of when a top-evaluation loop would be appropriate:

Top-Evaluation Loops


Chapter Contents






Hands-On Exercise 2.3 Exceptions




In your Exercise Manual, please refer to Hands-On Exercise 2.3: Programming Loops


Chapter Contents







Exceptions Hands-On Exercise 2.4


An exception is a message sent from a method in response to some invalid circumstance• Exceptions must be caught or the program will crash• Classes often throw exceptions if they are used incorrectly

Use the Throw keyword to activate the exception • Specify a message that explains why the exception was thrown• Often done in response to bad user input

Visual Basic code:

Exceptions

Public Property Operation() As String' Get clause omittedSet(value As String)Dim input As String = value.ToUpper().Substring(0, 1)If input = "A" Or input = "S" Or input = "M" Or input = "D" Then

_operation = inputElse

Throw New Exception _ ("Must enter Add, Subtract, Multiply or Divide")

End IfEnd Set

End Property

If the user enters invalid data, throw the exception

def·i·ni·tion


C# code:

Exceptions

public string Operation{

get{

return _operation;}set{

string input = value.ToUpper().Substring(0, 1);

if (input == "A" || input == "S" ||input == "M" || input == "D")_operation = input;

elsethrow new Exception("Must enter Add, Subtract, Multiply or Divide");

}}

If the user enters invalid data, throw the exception


Exceptions are handled with a Try-Catch error handler• Try to do something• If an exception is raised, Catch it

Can optionally have a Finally statement• Finally is for code that runs whether or not an exception is raised

Visual Basic code:

Try-Catch Exception Handling

Dim inputValid As Boolean = FalseDo

Console.WriteLine _("Do you want to (A)dd, (S)ubtract, (M)ultiply or (D)ivide?")

Trygame.Operation = Console.ReadLine()inputValid = True

Catch ex As ExceptionConsole.WriteLine(ex.Message)

End TryLoop While inputValid = False


C# code:

Try-Catch Exception Handling

bool inputValid = false;do{

Console.WriteLine("Do you want to (A)dd, (S)ubtract, (M)ultiply or (D)ivide?");

try{

game.Operation = Console.ReadLine();inputValid = true;

}catch (Exception ex){

Console.WriteLine(ex.Message);}

} while (inputValid == false);


Chapter Contents







Exceptions




In your Exercise Manual, please refer to Hands-On Exercise 2.4: Structured Exception Handling


You are now able to • Program in C# and Visual Basic

You have Investigated data types and type conversions Used If and Case statements to allow programs to make decisions Programmed loops Handled errors

Chapter Summary


What are the two types of numbers?

How would one decide whether to declare a variable as Integer or Long?

What does it mean to say that .NET is a type-safe environment?

How could a String be converted to an Integer?

What is implicit type conversion?



What constructs can be used for a decision-making statement?

What are the two types of loops?

When should a Try-Catch error handler be used?

Rewrite the following using a Select-Case or switch statement:


Dim pet As StringIf pet = "Dog" then

Feed("Bone")ElseIf pet = "Cat" then

Feed("Catsup")ElseIf pet = "Frog" then

Feed("ToCat")Else

Feed("Steak")End If


The C# language, see• Course 419, C# Programming

The Visual Basic language, see• Course 503, Visual Basic® Programming for .NET

Automated testing, see• Course 511, .NET Best Practices and Design Patterns

To Learn More About…

®

419503511

Programming Windows User Interfaces

Chapter 3


We delivered our Flash Cards program and it was exactly what they wanted.But now they want a slick graphical user interface. Oh well, such is the life of a programmer. The question is: With such a major change, are we going tohave to rewrite the whole program?

Open your Flash Cards program and answer the following questions:

Does the FlashCardsGame class have any user-interface code? • In other words, does it ever do a Console.WriteLine() or

Console.ReadLine()?

Where is all the user-interface code located?

So, do we have to rewrite the whole program? If not, what do we have to replace?

Those Ever-Changing Requirements


After completing this chapter, you will be able to • Program a Windows application with .NET

To accomplish this, you will Create a Windows-based user interface for Flash Cards Investigate event-driven programming Handle events from Windows forms and controls Declare and raise events from custom classes Retrieve user input with dialog forms

Chapter Objectives


Chapter Contents

Windows Forms Applications Overview


Event-Driven Programming


Raising Events


Dialogs



Consist of a series of forms, or screens• One form is the startup or controlling form• Forms can open or activate other forms• Forms have controls • Forms can have menus

Forms allow the user to retrieve and manipulate data• Each form displays data inside its controls• Menus and controls are used to save and retrieve data, create new records,

etc.

Windows Applications


Add forms to projects using Solution Explorer• Right-click the project and select Add | Windows Form• Give the form a name

Form names should be descriptive and follow a convention• FlashCardsForm

• Microsoft standard in .NET

Adding Forms to a .NET Project


Property DescriptionName The variable name used to refer to the formFormBorderStyle Determines border style and whether or not the form is sizableMaximizeBox Determines whether a maximize button is in the caption barMinimizeBox Determines whether a minimize button is in the caption barStartPosition Determines where the form should appear when loadedSize The size of the form in pixels (Height and Width)

Text Determines the caption of the form

WindowState Determines whether the form is maximized, minimized, or normal in size

AcceptButton The button whose Click event runs when the user presses <Enter>

Form Properties Some common properties of Windows forms

• Can be set from the Properties window • Can be set in code


Allows design of Windows forms with a WYSIWYG display• Controls are dragged from the Toolbox and positioned on the screen• Automatically generates the code in the background• Components with no

visual representation are displayed in the tray at the bottom of the form

Windows Forms Designer

WYSIWYG = what you see is what you get


Toolbox

Allows drag-and-drop access to common controls and components• Organized as a series of tabs• Tabs can be expanded and collapsed • Tabs change depending on the type of application


Allows for setting control properties at design time• Generates code inside the code window as properties are set• List of properties is dynamic depending on the control selected

Allows properties to be set only to appropriate data types• Includes various drop-downs and

dialogs that make setting property values easier

• Double-click to walk around preset choices

Properties Window


Controls are dragged from the Toolbox and dropped on the form• Positioned and sized on the screen with the mouse

Controls should be given descriptive names• PlayButton, AddRadioButton, AnswerTextBox, etc.

All controls work in a similar way with many properties in common• Each control also has properties specific to itself

Adding Controls to a Form


Common properties of controls• Can be set from the Properties window• Can be set in code• Most properties can be changed at design time or runtime

Control Properties

Property DescriptionName The name used in code to identify the objectText The text contained in the controlLocation The position of the top left corner of the control with respect to its form

Size The size of the control in pixels (could also use Height and Widthproperties)

Font The font used to display text in the controlTabIndex Determines the Tab order of the control


Drag the MenuStrip control from the Toolbox onto the form• Icon is displayed in the tray at the bottom of the form• Form’s MainMenuStrip property is set to the MenuStrip control’s name

To create menu items• Click the MenuStrip control• Type the menu text• Use the arrow keys to move

up, down, left, and right

Menu items are named based on their text• File menu is automatically

named FileToolStripMenuItem

Adding a Menu to a Form


To create access keys, prefix any letter with the ampersand character (&) • User can select that item by typing the underlined letter• For top-level items, press the <Alt> key and type that letter

Can also set ShortcutKeys property• Pick a shortcut key and set the ShowShortcutKeys property to True

Properties of menu items:

Menu Items

Property DescriptionName The name used in code to identify the menu itemText The text of the menu item. Prefix any letter with the &

character to underline that character and create an access keyChecked Set to True or False to put a checkmark next to that itemShortcutKeys The shortcut keys on the keyboard that selects the menu itemShowShortcutKeys Determines whether the shortcut key is displayed when the

menu is expanded


Use project properties to change the application type to Windows Forms• Still requires an entry point that starts the controlling form

Call System.Windows.Forms.Application.Run() to start the program• Pass a new instance of the controlling form as an argument to Run() method• Closing that form will stop the program

Starting a Windows Application

System.Windows.Forms.Application.Run(new FlashCardsForm());


A form is a class that knows how to display itself on the screen• Properties determine how the form looks• Methods allow it to be displayed on or removed from the screen• Events are raised as the user interacts with the form

To open a form• Declare a variable of the form’s type

– Use the New keyword to create an instance of the form• Call the form object’s Show() method to display it on the screen


Opening Forms

Dim frm As New FlashCardsFormfrm.Show()

FlashCardsForm frm = new FlashCardsForm();frm.Show();


Chapter Contents


Hands-On Exercise 3.1 Event-Driven Programming


Raising Events


Dialogs




In your Exercise Manual, please refer to Hands-On Exercise 3.1: Designing Windows Forms


Chapter Contents



Event-Driven Programming Hands-On Exercise 3.2

Raising Events


Dialogs



An event is a message sent from controls or other objects• Some action causes an event to be raised• Programmer can choose to respond to the event or not

Windows applications run in a loop waiting for something to do• Events are raised• If an event handler exists, the code inside that function runs

Examples of events:• User clicks a button and that button’s Click event is raised• User clicks a menu item and that menu item’s Click event is raised• A form is shown on the screen and its Load event is raised

Many more events are raised than one would write event handlers for

Events def·i·ni·tion


Form Events

Forms raise many events• When they are displayed• When they are closed• When they receive or lose the focus

Common form events:

Event DescriptionLoad Occurs before the form is displayed for the first time; used to initialize

the controls and variables of a formFormClosing Occurs when a request to close the form is received but before the

form is actually closed; gives user an opportunity to cancel the requestFormClosed Occurs when the form is closedActivated Occurs when the form receives the focus


Control Events

Depending on the type of control, many different events are commonly used

Common control events:

Event DescriptionClick Occurs when the mouse is clicked on the controlDoubleClick Occurs when the mouse is double-clicked on the controlTextChanged Occurs when the text in a textbox changesValidating Occurs when a textbox or other control loses focus, but

only if the control’s text or value has changedSelectedIndexChanged Occurs when the selected item in a list box or combo box

changesCheckedChanged Occurs when a checkbox is checked or unchecked


An event handler is a function that runs in response to an event being raised

Controls have many events, but one is always assigned as the default• Not surprisingly, the default is usually the one that is used• Creating event handlers is usually automated by the designer

To create an event handler for a control or form, double-click it• The code window opens, and an event handler is created• The event handler handles the default event

Visual Basic code:

Event Handlers

This function handles the Click event of the Play button

def·i·ni·tion


C# code:

Event Handlers

this.PlayButton.Click += new System.EventHandler(this.PlayButton_Click);

In C#, this line of code is generated to specify the function to run when the event is raised


To create an event handler for an event that is not the default• Click the lighting bolt in the

Properties window• Double-click the event

Creating Non-Default Event Handlers

Click here to see all the events for a control

Double-click an event to generate the event handler


Chapter Contents




Hands-On Exercise 3.2 Raising Events


Dialogs




In your Exercise Manual, please refer to Hands-On Exercise 3.2: Programming Windows Events


Chapter Contents





Raising Events Hands-On Exercise 3.3

Dialogs



Someone had a good idea that students should be able to accumulate points as they answer questions correctly. For each correct answer, 10 points will be added to the student’s score. This should be displayed on the screen.

Let the FlashCardGame class maintain the current score• Program this class to raise an event when the score changes• The event would be received by the user interface• The user interface would have an event handler that updates the score



1. Declare the event• Event names should be appropriate to the action that has occurred • Click, Load, TextChanged, ScoreChanged, etc.

2. Raise the event at the appropriate time• The ScoreChanged event will be raised in the Score property’s setter

Steps to Programming Events


Declaring the event exposes it outside the class• Events are declared at the class level• Use the Event keyword• The data type of the event defines the arguments required by event handlers

EventHandler data type is the default data type for events• Requires two arguments, sender and an event argument e

Visual Basic code:

C# code:

Declaring an Event

Public Event ScoreChanged As EventHandler

public event EventHandler ScoreChanged;


Use the RaiseEvent keyword• Specify the event name

Supply the arguments• Sender and event argument• The sender is always the current instance of the class (Me)• By default, the event argument is empty

Visual Basic code:

Raising an Event in Visual Basic

Public Property Score() As IntegerGet

Return mScoreEnd GetSet(value As Integer)

mScore = value

RaiseEvent ScoreChanged(Me, EventArgs.Empty)End Set

End Property


Call the event as if it were a function of that name• if statement required to ensure at least one event handler has been created

Supply the arguments• Sender and event argument• The sender is always the current instance of the class (this)• By default, the event argument is empty

C# code:

Raising an Event in C#

public int Score{

get{ return mScore; }set{

mScore = value;

if (ScoreChanged != null){

ScoreChanged(this, EventArgs.Empty);}

}}


Chapter Contents





Raising Events

Hands-On Exercise 3.3 Dialogs




In your Exercise Manual, please refer to Hands-On Exercise 3.3: Declaring and Raising Events


Chapter Contents





Raising Events


Dialogs Hands-On Exercise 3.4


A dialog form is a form that is used to query the user for information

Typical dialog form properties:

Dialog Forms

Property Value Description

FormBorderStyle FixedDialog Determines the border of the form; FixedDialog style cannot be resized

AcceptButton OK or Open button The button that is “clicked” when the user presses the <Enter> key

CancelButton Cancel or Close button The button that is “clicked” when the user presses the <Esc> key

ControlBox False Determines whether the form has a control box; usually turned off for a dialog

MinimizeBox False Determines whether the form has a minimize button

MaximizeBox False Determines whether the form has a maximize button

StartPositionCenterScreen or CenterParent

Determines where the form is displayed on the screen

def·i·ni·tion


Displays a form on the screen modally• This means code execution will stop until the form is closed• After the form is closed, retrieve the values from its controls


ShowDialog() Method

UserDialogForm userDialog = new UserDialogForm();userDialog.ShowDialog();game.User = userDialog.UserTextBox.Text;this.WelcomeLabel.Text = "Hello " + game.User;

Dim userDialog As New UserDialogFormuserDialog.ShowDialog()game.User = userDialog.UserTextBox.TextMe.WelcomeLabel.Text = "Hello " + game.User


A value can be assigned to a button’s DialogResult property• If set to anything but None, clicking the button will close a form that is

displayed with the ShowDialog() method• The form’s ShowDialog() method returns the value of the DialogResult

property

DialogResult property values come from the DialogResultenumeration• Values are Abort, Cancel, Ignore, No, None, OK, Retry, Yes

DialogResult Property

I’ll meet you at the airport baggage claim!

OK, bye.


Can use the FormClosing event of the form to ask the user if they are sure

Use the MessageBox.Show() method to query the user• Specify which buttons should be included with the message box• The button clicked returns from the Show() method

Use an If statement to cancel the action if the user is not sure• Cancel property is included in the CancelEventArgs argument of the FormClosing event

Collecting User Input with MessageBox



Collecting User Input with MessageBox Examples


Chapter Contents





Raising Events


Dialogs




In your Exercise Manual, please refer to Hands-On Exercise 3.4: Using a Dialog Form to Retrieve User Input


You are now able to • Program a Windows application with .NET

You have Created a Windows-based user interface for Flash Cards Investigated event-driven programming Handled events from Windows forms and controls Declared and raised events from custom classes Retrieved user input with dialog forms

Chapter Summary


What does a Windows application consist of?

What method is used to display a form on the screen?

What are some of the standard Windows controls?

What is the difference between an event and an event handler?

What does it mean to display a form modally? How is this done?



Windows Presentation Foundation, see• Course 975, WPF and Silverlight® Introduction


®

975

Object-Oriented Programming

Chapter 4


After completing this chapter, you will be able to • Create a .NET class library to allow for code reuse

To accomplish this, you will Separate responsibilities into multiple classes for easier maintenance Use inheritance to simplify application logic Create a Class Library project in Visual Studio

Chapter Objectives


After delivering the Windows version of Flash Cards, we received some feedback from the customer

They decided multiplication is too hard; for multiplication, the random numbers should be between 0 and 12

For division, they want us to rig the numbers so that the students always get a question that will result in a whole number between 1 and 9

Customer Feedback

∑Xii=1X =

n

ŋ


Chapter Contents

The Single Responsibility Principle Hands-On Exercise 4.1

Inheritance


Class Libraries



The Single Responsibility Principle states that a class should do one job• A class should have only one reason to change

Examples:• A class that displays data to a user should not also talk to a database• A class that saves and retrieves data from a database should not know anything

about how that data is represented to the user• Complex business processing, data validation, or transactions should be

encapsulated within some controlling class

• How might following this principle make programs easier to maintain?

Single Responsibility Principle def·i·ni·tion


In the current version of FlashCards, there are two classes:• FlashCardsForm defines the user interface• FlashCardsGame maintains the game

Current FlashCards Classes


In the case study, another class called NumberGenerator will be added• Responsible only for generating the random numbers for the FlashCardsGame class

• An instance of FlashCardsGame is passed to it • It sets that instance’s Number1 and Number2 properties

VB code:

Coding the NumberGenerator Class

Public Class NumberGenerator

Public Sub GenerateNumbers(flashcard As FlashCardsGame)Dim randomNumber As _New Random(DateTime.Now.Millisecond)

flashcard.Number1 = randomNumber.Next(0, 99)flashcard.Number2 = randomNumber.Next(0, 99)

End Sub

End Class


C# code:

Coding the NumberGenerator Class

public class NumberGenerator{

public void GenerateNumbers(FlashCardsGame flashcard){

Random randomNumber =new Random(DateTime.Now.Millisecond);

flashcard.Number1 = randomNumber.Next(0, 99);flashcard.Number2 = randomNumber.Next(0, 99);

}}


An instance of NumberGenerator is created in FlashCardsGame• FlashCardsGame must pass a reference to itself when using it

VB and C# code:

Using the NumberGenerator Class


‘ Code omittedPublic Sub GenerateNumbers()

Dim generator As NumberGeneratorgenerator = New NumberGenerator()generator.GenerateNumbers(Me)

End Subpublic class FlashCardsGame{

// Code omittedpublic void GenerateNumbers(){

NumberGenerator generator;generator = new NumberGenerator();generator.GenerateNumbers(this);

}}


Me in Visual Basic or this in C# refers to the current instance of a class• More explicit when referring to a member of a class from within that class• Can be used to pass a reference of the current class to an external function• Used when raising events (represents the sender)

VB code:

Me (this) Keyword

Public Sub New(operation As String)

Me.Operation = operationEnd Sub

Public Sub GenerateNumbers()Dim generator As NumberGeneratorgenerator = New NumberGenerator()

generator.GenerateNumbers(Me)End Sub

RaiseEvent ScoreChanged(Me, EventArgs.Empty)


C# code:

Me (this) Keyword

public FlashCardsGame(string operation){

this.Operation = operation;}


NumberGenerator generator;generator = new NumberGenerator();

generator.GenerateNumbers(this);}

if (ScoreChanged != null){

ScoreChanged(this, EventArgs.Empty);}


A constructor is a function that runs automatically when a class is instantiated• In VB, the constructor is a subroutine named New• In C#, the constructor is a function with no return type (not even void), with the

same name as the class

When an instance of a class is created, properties may need to be initialized• Especially fields accessed via read-only properties • Initialization is done inside the class’s constructor

Visual Basic code:

Constructors


Public Sub New(operation As String)Me.Operation = operation

End Sub…

def·i·ni·tion


C# code:

Constructors

public class FlashCardsGame{

public FlashCardsGame(string operation){

this.Operation = operation;}

…


Chapter Contents

The Single Responsibility Principle

Hands-On Exercise 4.1 Inheritance


Class Libraries




In your Exercise Manual, please refer to Hands-On Exercise 4.1: Coding the NumberGenerator Class


Chapter Contents



Inheritance Hands-On Exercise 4.2

Class Libraries



Inheritance allows a class to reuse and extend functionality of another• The base class provides the reusable behavior• The derived class can add new behaviors or change the existing behaviors

Inheritance, when used correctly, can• Reduce code duplication• Reduce complexity• Make testing easier


Inheritance

Public Class MultiplicationNumberGenerator

Inherits NumberGenerator

End Class

def·i·ni·tion

public class MultiplicationNumberGenerator : NumberGenerator{

}


1. Reduce code duplication• Sometimes a program has multiple classes with similar fields, properties,

and methods• Add a base class and move the common behaviors to that class• Have each class inherit from the base class

2. Reduce complexity• Sometimes a class has a variable that affects its behavior• If statements within the class check the variable and do things differently

based on its value– This makes using, understanding, and testing the class more difficult

• Add a derived class for each type and move the conditional logic

Two Reasons to Use Inheritance


NumberGenerator class calculates numbers for Addition and Subtraction

Derived classes override the GenerateNumbers() method for multiplication and division

Inheritance Hierarchy


A virtual method is one that is programmed in the base class but can be changed in the derived class if necessary• The base class has default functionality

Visual Basic code:• Use the Overridable keyword in the base class• Use the Overrides keyword in the derived class

Virtual Methods

Public Class NumberGenerator

Public Overridable Sub GenerateNumbers(flashcard As FlashCardsGame)Dim randomNumber As _

New Random(DateTime.Now.Millisecond)


End SubEnd Class

Public Class MultiplicationNumberGeneratorInherits NumberGenerator

Public Overrides Sub GenerateNumbers(flashcard As FlashCardsGame)Dim randomNumber As _New Random(DateTime.Now.Millisecond)


End SubEnd Class

def·i·ni·tion


C# code:• Use the virtual keyword in the base class• Use the override keyword in the derived class

Virtual Methods

public class NumberGenerator{

public virtual void GenerateNumbers(FlashCardsGame flashcard){


flashcard.Number1 = randomNumber.Next(0, 99);flashcard.Number2 = randomNumber.Next(0, 99);

}

public class DivisionNumberGenerator : NumberGenerator{

public override void GenerateNumbers(FlashCardsGame flashcard){


int temp;temp = randomNumber.Next(1, 9);flashcard.Number2 = randomNumber.Next(1, 12);flashcard.Number1 = temp * flashcard.Number2;

}}

def·i·ni·tion


The program must decide which number generator to use• The variable uses the base class type in its declaration• Any type of NumberGenerator can be assigned to that variable

VB and C# code:

Constructing the Correct Class

Public Sub GenerateNumbers()

Dim generator As NumberGenerator

Select Case Me.OperationCase "M"

generator = New MultiplicationNumberGenerator()Case "D"

generator = New DivisionNumberGenerator()Case Else

generator = New NumberGenerator()End Select

generator.GenerateNumbers(Me)End Sub


C# code:

Constructing the Correct Class


NumberGenerator generator;

switch (this.Operation){

case "M":generator = new MultiplicationNumberGenerator();break;

case "D":generator = new DivisionNumberGenerator();break;

default:generator = new NumberGenerator();break;

}generator.GenerateNumbers(this);

}


Chapter Contents



Inheritance

Hands-On Exercise 4.2 Class Libraries




In your Exercise Manual, please refer to Hands-On Exercise 4.2: Inheriting From the NumberGenerator Class


Chapter Contents



Inheritance


Class Libraries Hands-On Exercise 4.3


A class library is an application that contains reusable classes but cannot be executed on its own• Compiled with the .dll file extension• There is no entry point• Can be accessed only from some other running program

Reasons to use class libraries:1. Allow the classes to be reused in multiple applications2. Allow for better organization of classes, especially on large projects3. Can be easier for multiple developers or multiple teams to divide work

Class Libraries


Steps:1. Right-click your solution in Solution Explorer2. Select Add | New Project3. Choose your preferred language4. Select Class Library from the list of templates

Creating a Class Library Project


To use the classes in a library from another project, set a reference to it• This copies the .dll file into that project’s bin folder

Steps:1. Right-click the project in Solution Explorer and select Add Reference2. In the Add Reference dialog, choose the Projects tab3. Choose the library from the list

Setting References


Adding Imports (VB) or using (C#) to the top of a code file allows a class to be used without specifying its namespace• Refer to the class as though it was a part of the current project

Visual Basic code:

C# code:

Imports (using)

Imports FlashCardsLibrary

Public Class FlashCardsFormPrivate WithEvents game As New FlashCardsGame' code omitted

End Class

using FlashCardsLibrary;namespace FlashCards{

public partial class FlashCardsForm : Form{

private FlashCardsGame game = new FlashCardsGame();// code omitted

}}


Chapter Contents



Inheritance


Class Libraries




In your Exercise Manual, please refer to Hands-On Exercise 4.3: Creating the FlashCards Library


You are now able to • Create a .NET class library to allow for code reuse

You have Separated responsibilities into multiple classes for easier maintenance Used inheritance to simplify application logic Created a Class Library project in Visual Studio

Chapter Summary


Define the Single Responsibility Principle:

Define a constructor:

Give two reasons to use inheritance:

List some advantages of class libraries:



The programming process, analysis, and class design, see• Course 933, Agile Software Development and Modeling


®

933

Designing Web User Interfaces With ASP.NET

Chapter 5


We delivered our Windows version of the Flash Cards application, and it was exactly what they wanted. But now they want a web version that runs in a browser.

With such a major change, are we going to have to rewrite the whole program?

What can be reused?



After completing this chapter, you will be able to • Create a web application using ASP.NET

To accomplish this, you will Create an ASP.NET Web Application project in Visual Studio Construct Web Forms user interfaces Process user requests over the web Allow users to create accounts and log in using Web Forms Authentication Style ASP.NET websites using Cascading Style Sheets

Chapter Objectives


Chapter Contents

Creating Web Applications Hands-On Exercise 5.1

Processing ASP.NET Web Forms


Web Forms Security


Styling ASP.NET Applications



Use standard Internet protocols• TCP/IP to connect to the Internet• HTTP for web requests and responses

Require a web server• Web servers handle all HTTP requests• Applications are configured under IIS

Web server waits for user requests• Returns web pages to the browser

Web Applications

HTTP = Hypertext Transfer ProtocolIIS = Internet Information ServicesTCP/IP = Transmission Control Protocol/Internet Protocol


Web applications return data in three languages to the browser:1. HTML (HyperText Markup Language)2. CSS (Cascading Style Sheets)3. JavaScript

HTML is used to describe the page content• Headings are used to emphasize content• <div> and <p> tags are used to organize content• <form> and <input> elements are used to collect information• <a> elements are used to create hyperlinks to other pages

CSS is used to style page content• Fonts, colors, size, and positioning should all be done using CSS

JavaScript is used to add dynamic behaviors to web pages• JavaScript is downloaded to the browser as raw text• The browser compiles and executes the JavaScript code

Web Application Languages


HTML is a text-based markup language used to format data in a browser

Page is divided into two sections• Head is used for title and certain non-visible elements• Body contains the formatted data displayed to the user

Elements determine how text should be formatted• Each element has an opening and closing tag

HTML

Opening tag

def·i·ni·tion

<a href="Default.aspx">Home</a>

Tag valueValue of tag attribute

Closing tagTag attribute


Contain controls that allow users to send data back to the server• Controls include text boxes, list boxes, drop-downs, checkboxes, radio

buttons, submit buttons, and reset buttons

Have two main attributes:• action attribute determines where the form is submitted• method attribute determines how the control values are submitted

Input element is used to create controls inside the form

HTML Forms

<form method="post" action="Login.aspx">User name:<input type="text" /><br />Password:<input type="password" /><br /><br /><input type="submit" value="Login" />

</form>


Some Common HTML Tags

Tag Description<html></html> Surround the entire HTML page<head></head> At the top of the page; includes the title, which is displayed in the

title bar of the browser<body></body> Below the head; includes the text displayed to the user<h1></h1> Heading 1; used for large, bold text suitable for a heading; also,

h2, h3, h4, h5, and h6

<p></p> Paragraph tag; used to separate text. Inserts a blank line<br /> Break; used to move to a new line, but does not insert a blank

line<form></form> Contains HTML text boxes, drop-downs, checkboxes, radio

buttons, and list boxes for building an input/output form<input /> Used to create input fields on forms. Type attribute is set to

text, password, radio, checkbox, submit, reset, etc.<a></a> Anchor tag used to create hyperlinks; href attribute determines

the URL to the link; value determines the text that is underlined

URL = uniform resource locator


Sample HTML Page<html xmlns="http://www.w3.org/1999/xhtml"><head>

<title>Login</title></head><body>

<h1>Ralph's Pretty Good Web site!</h1><a href="Default.aspx">Home</a><br /><br /><form method="post" action="Login.aspx">User name:<input type="text" /><br />Password:<input type="password" /><br /><br /><input type="submit" value="Login" /></form>

</body></html>


Simplify web application development• HTML is automatically generated• Form input is automatically retrieved

Web Forms controls are used to design pages• Just drag and drop on the form• Processing is done much like Windows applications

Require the .NET Framework on the server

IIS software must also be installed on the web server• Routes requests for pages with the .aspx extension to .NET for processing

ASP.NET Applications


Steps:1. Right-click solution in Solution Explorer and select Add | New Project2. Choose the preferred language and the web branch of the tree view3. Choose ASP.NET Web Application from the list of templates4. Specify an appropriate name and folder location for the web project files

Creating ASP.NET Projects With Visual Studio


There are multiple frameworks that can be used within ASP.NET• ASP.NET Web Forms • ASP.NET MVC• Web API

These frameworks can be used independently or together

This class will useASP.NET Web Forms

ASP.NET Templates


Includes predefined default pages and resources• Default master page• Home page• About and contact pages• Pages for registering and logging in• Default theme and style sheet• Commonly used JavaScript files• Etc.

ASP.NET Web Forms Application Template


Managing Web Projects With Solution Explorer

ASP.NET projects work a little differently than Windows programs• Code is executed on the server• The ASP.NET code generates HTML, CSS,

and JavaScript• Sends the results back to the browser

Web projects can contain• Web pages with the .aspx file extension

– Each page has a code-behind file in VB or C#

• Databases, placed in the App_Data folder• Other resources, such as graphics, style

sheets, and JavaScript files


Are like a template for all other pages in a website• If a web form uses a master page, all the master page content is included• If master page content changes, it is automatically reflected in the web form• Headers, footers, menus, and links are examples of things to put on the

master page

Page-specific content will be placed in a ContentPlaceHolder element• Content placeholders can be in the HTML <head> and <body>• Any number of content placeholders can be added to the master page

Master Pages


Sample Master Page


Are used to generate web pages in ASP.NET• Require .aspx file extension• Contain one <form></form> element• Form is always submitted to itself• All controls on the web page are contained within the form

To create a web form• Right-click the web project

in Solution Explorer• Select from the menu

Add | New Item• Select the “Web Form with

Master Page” template• Give the web form an

appropriate name• Will be prompted to select

the Master Page

Web Forms


Dragged and dropped from the Toolbox onto the web form page• Names and properties are

very similar to Windows controls

• Programmed like Windows controls

Automatically generate HTML that is sent to the browser

Web Form Controls

Click Source to view the ASP.NET markup. Click Split to show both the markup and Design views.


FlashCards will include the following:

Site.master

• The master page for all other pages

Default.aspx

• The FlashCards home page

Login.aspx

• Lets the user log in to the application

Register.aspx

• Allows new users to create accounts

FlashCards.aspx

• Allows the user to play the game• Very similar to the Windows version

Web Forms for the FlashCards Website


FlashCards Web Pages


Chapter Contents

Creating Web Applications

Hands-On Exercise 5.1 Processing ASP.NET Web Forms


Web Forms Security






In your Exercise Manual, please refer to Hands-On Exercise 5.1: Creating an ASP.NET Web Application


Chapter Contents



Processing ASP.NET Web Forms Hands-On Exercise 5.2

Web Forms Security





ASP.NET processing is event-driven in the same way as Windows applications• Web forms must be submitted back to the server for the events to fire

Web page has events that are fired on each request

Web form controls have events just like their Windows counterparts• For example, the ASP.NET Button control raises a Click event

Can handle any other events as needed• For example, the FlashCards.aspx page will handle the FlashCardsGame

class ScoreChanged event

Property values of ASP.NET controls can be retrieved and updated in the same ways as with Windows Forms

Web Forms Processing With Events


Page’s Load event is used to process pages• Raised every time the page is requested• Also occurs when the form is submitted• IsPostback property determines if the form is being requested the first time

IsPostback equals false when the page is being requested via a hyperlink• Controls should be initialized only on the first request

IsPostback equals true when the user has submitted the form• Process the form submission

Visual Basic code:

Processing Web Forms

Protected Sub Page_Load(sender As Object…If IsPostBack = False Then

QuestionLabel.Text = ""game.User = "Joe"WelcomeLabel.Text = "Hello " + game.User + "."

ElseFormSubmitted()

End IfEnd Sub


C# code:

Processing Web Forms

protected void Page_Load(object sender, EventArgs e)

{ if (IsPostBack == false){

QuestionLabel.Text = "";game.User = "Joe";WelcomeLabel.Text = "Hello " + game.User + ".";

}else{

FormSubmitted();}

}


Web pages are completely destroyed after each request is processed• Need a way to store user variables that need to live beyond a single request

Session variables allow information to be stored for each user• Available to every web form in the application• Each user has his or her own copy of each Session variable• Session variables are destroyed on the server after a period of inactivity

– By default 20 minutes

Creating and accessing Session variables is done using name–value pairs• Value of a Session variable can be of any data type

User Variables

VB: Session("VariableName") = SomeValue

C#: Session["VariableName"] = SomeValue;


Visual Basic code for using a Session variable:

C# code for using a Session variable:

Creating and Retrieving Session Variables

If Session("FlashCardsGame") Is Nothing Thengame = New FlashCardsGame()Session("FlashCardsGame") = game

Elsegame = Session("FlashCardsGame")

End If

Create the Sessionvariable

Retrieve the variable

if (Session["FlashCardsGame"]== null){

game = new FlashCardsGame();Session["FlashCardsGame"] = game;

}else{

game = (FlashCardsGame)Session["FlashCardsGame"];}

Create the Sessionvariable

Retrieve the variable


Chapter Contents




Hands-On Exercise 5.2 Web Forms Security






In your Exercise Manual, please refer to Hands-On Exercise 5.2: Programming ASP.NET Web Forms


Chapter Contents





Web Forms Security Hands-On Exercise 5.3




Is used to control access to a website• Configured in the Web.config file• Access rules are used to set permissions on folders

The ASP.NET template preconfigures Web Forms security

ASP.NET Web Forms Security


Determine who has the rights to view pages in the website folder• Defined within a Web.config file in each folder that requires security• Forces someone to log in before accessing pages within this folder• All pages in a folder should have the same access rules

Can allow or deny users based on username or role

Example access rule:

Access Rules

<?xml version="1.0" encoding="utf-8"?><configuration>

<system.web><authorization>

<deny users="?" /></authorization>

</system.web></configuration>


Once access rules are defined, anonymous users are automatically redirected to Login.aspx• Login control generates

the page

After logging in, users are redirected to the page they originally requested• Notice the variable

embedded in the URL

Login Page


Need to identify who the user is

Can be accessed via the User class• User.Identity.Name returns the user’s name


Identifying Users

Protected Sub Page_Load(sender As Object…

If IsPostBack = False ThenQuestionLabel.Text = ""WelcomeLabel.Text = "Hello " + User.Identity.Name

End IfEnd Sub

protected void Page_Load(object sender, EventArgs e){

if (IsPostBack == false){

QuestionLabel.Text = "";

WelcomeLabel.Text = "Hello " + User.Identity.Name;}

}


Chapter Contents





Web Forms Security

Hands-On Exercise 5.3 Styling ASP.NET Applications




In your Exercise Manual, please refer to Hands-On Exercise 5.3: Web Forms Security


Chapter Contents





Web Forms Security


Styling ASP.NET Applications Hands-On Exercise 5.4


CSS styles control formatting of all HTML pages• Fonts, colors, graphics, positioning, and even behaviors can be controlled

inside style sheets

Styles consist of• Cascading Style Sheets (CSS) • Graphics that are applied by the styles

A default style is added by the template• Can customize the CSS or create a

completely new theme

The styles are loaded by the master page

ASP.NET Styles


Are text files that contain styles that can be applied to any HTML tag• Each CSS file is downloaded to the browser and the styles are applied• CSS is a W3C standard supported by all

browsers

Style rules can be created for any HTML element• Attributes and values are defined in the rule• These are then added to each instance of the

HTML element by the browser

Rules consist of• Selectors that determine which elements the

style will be applied to• Curly braces delimit the styles• Attributes and values separated by colons• Each attribute/value pair ends with a semicolon

Cascading Style Sheets

W3C = World Wide Web Consortium


CSS Selector Examples

a {color: #333;text-decoration: underline;

}input, textarea{

color: #333;font-size: 1.2em;width: 300px;

}input[type="radio"] {

background: transparent;left: 125px;

}.score {

font-size: xx-large;color: red;

}#question {

font-size: xx-large;vertical-align: top;

}

Selectors determine which elements a style is applied to• Can be all elements of some type• Comma can be used to specify multiple

elements• Square brackets [ ] can be used to select

elements with a particular attribute value• Prefixing a selector with a period selects

elements whose class attribute is set to that value

• Prefixing a selector with a pound sign (#) selects elements whose id attribute is set to that value


In the CSS file, right-click one of the style elements and select Build Style• This opens the Modify Style dialog

The Modify Style dialog provides a graphical interface for specifying attributes and their values

Creating Styles

Preview the effect of the style

Select the appropriate category


Styling for Mobile Devices

The default CSS file includes style rules for mobile devices• Uses a CSS media query to select

devices with small screens• Allows ASP.NET applications to look

good on mobile phones by default


The theme is applied to the website inside the master page file• Done in the <head></head> element

Applying the Theme to the Website

<head runat="server"><meta charset="utf-8" /><title>Flash Cards <%: Page.Title %> </title><asp:PlaceHolder runat="server">

<%: Scripts.Render("~/bundles/modernizr") %></asp:PlaceHolder>

<webopt:BundleReference runat="server" Path="~/Content/css" /><link href="~/favicon.ico" rel="shortcut icon" type="image/x-icon" />

</head>


Chapter Contents





Web Forms Security






In your Exercise Manual, please refer to Hands-On Exercise 5.4: Styling Sites With CSS


You are now able to • Create a web application using ASP.NET

You have Created an ASP.NET Web Application project in Visual Studio Constructed Web Forms user interfaces Processed user requests over the web Allowed users to create accounts and log in using Web Forms Authentication Styled ASP.NET websites using Cascading Style Sheets

Chapter Summary


In web applications, requests are made via which protocol?

What language is used to display data in a browser?

What HTML tag is used to allow a user to send data to a web server?

What would be the syntax for a link to Microsoft’s website?



In .NET, what technology is used to create web applications?

What property of the page object determines if the form was submitted?

What ASP.NET object is used to create user variables?

To force all users of a website to create an account, what access rule would be written?



Developing web applications, see• Course 2621, Building ASP.NET Web Applications• Course 977, Building Web Applications with ASP.NET MVC


®

2621977

Saving Data With Relational Databases

Chapter 6


We delivered our ASP.NET version of the Flash Cards application and it was exactly what they wanted. But then the customers had a meeting to talk about the program.

The teachers want to be able to review what the students are working on and what they are getting right and wrong. They want every flash card to be saved, along with the student’s answer.

They also decided that they wanted students to be able to accumulate points over time. When the students log in, they want the program to show them their lifetime statistics and score, as well as the score of the current game.

• What are we going to need to accomplish these requirements?



After completing this chapter, you will be able to • Program a database application in .NET

To accomplish this, you will Create a SQL Server database Write SQL queries to create, retrieve, update, and delete database data Execute SQL queries using Entity Framework code Automate the display of data on a web page using ASP.NET data binding

Chapter Objectives

SQL = structured query language


Chapter Contents

Creating SQL Server DatabasesWith Visual Studio


Database CRUD

Creating and Updating Records With Entity Framework


Retrieving Records


Data Binding With ASP.NET



Databases make data access efficient and secure• Fast searches and sorts• Record locking for multi-user access• Security by user or group

Relational databases contain• Tables• Indexes• Relationships

Relational Database Systems


SQL Server databases can be created using Solution Explorer1. Right-click the App_Data folder of the project and select Add | New Item2. Select SQL Server Database from the list of templates3. Name the database appropriately

The database then is displayed in Server Explorer

Creating a SQL Server Database


Visual Studio Server Explorer

Provides access to resources on a network server or the local machine• Log files• Services• Performance counters• And more

Use Server Explorer to access SQL Server databases• Tree lists all databases set up on the SQL

server• Each database can be expanded to view

tables and fields• Right-click the table and select “Show Table

data” to view the table’s records

Can access any other type of database, as well


Once created, the new database is included in the tree• Expand the database• Right-click the Tables branch and select Add New Table• This opens the Table Designer

Creating Tables


Fields are defined for each row• Enter field name under Name• Specify the data type from the

drop-down• Add any constraints and properties

for each field

Constraints and properties:• Length specifies maximum field

length• Allow Nulls checkbox determines if

the field can be empty • Default Value is used if a value is

not specified when the record is added

Table Designer


The SQL Server data types used in FlashCards are as follows• There are many other SQL Server data types

SQL Server Data Types

Data type Descriptionnvarchar Used to hold strings; set the Length to determine the

maximum size of the string in the fielddatetime Used for dates and includes the timeint Used to store whole numbers. Equivalent to a .NET

32-bit Integerfloat Used for real numbers. Closest equivalent to a .NET

Double


A primary key is a constraint that guarantees each row in a table is unique• Consists of one or more indexed fields• “Allow Nulls” must be false• Can set “Is Identity” field to True to create a counter

Right-click the field and select Set Primary Key• A primary key index is automatically created for that field• Allow Nulls checkbox is cleared• Identified by the key icon next to the field

Creating the Primary Key


Right-click Indexes on the right side of the Table Designer and select Add New | Index• Give the index a descriptive name• Click the ellipsis (…) next to the Columns property in the Properties window• Add the fields to be included in the index and set their sort order

Adding Indexes


Setting Index Properties Illustrated


The Table Designer is really generating an SQL script• Can be saved or executed against the database within Visual Studio• Can edit the SQL code directly if required

SQL Script


Click the Update button on the Table Designer to execute the script• Will add the new table and indexes to the database

Executing the Script


Chapter Contents

Creating SQL Server Databases With Visual Studio

Hands-On Exercise 6.1 Database CRUD



Retrieving Records






In your Exercise Manual, please refer to Hands-On Exercise 6.1: Creating a SQL Server Database


Chapter Contents



Database CRUD Creating and Updating Records

With Entity Framework


Retrieving Records





SQL is the standard language used by all databases, for all modifications• Creating, changing, or deleting tables and indexes• Adding users or groups• Inserting, updating, and deleting data• And much more

Application developers need to know how to do four things with SQL:• Create records• Retrieve records• Update records• Delete records

Structured Query Language (SQL) def·i·ni·tion


SQL Insert query is used to add records to the database

An Insert example for a SQL Server database:

• Scores is the table to add a record to• Followed by the fields in the table to be set• Followed by the values to set the fields to

In this example, values are passed as parameters• {#} used as placeholders for the parameters that will be passed• Parameter values are set in code before running the query

Creating Records

INSERT INTO Scores (UserName, QuestionTime, Equation, CorrectAnswer, StudentAnswer, Points) VALUES ({0}, {1}, {2}, {3}, {4}, {5})


SQL Select query is used to retrieve records from the database

Use the asterisk (*) to get all the fields from the table

Specify the fields if all of them are not required

Use the Where clause to filter the records• Again, a parameter is used to pass a value to the database

To sort the records, add the Order By clause

Retrieving Records

SELECT CorrectAnswer, StudentAnswer, Points FROM Scores

SELECT * FROM Scores

SELECT CorrectAnswer, StudentAnswer, Points FROM Scores WHERE UserName = {0}

SELECT CorrectAnswer, StudentAnswer, Points FROM Scores WHERE UserName = {0} ORDER BY QuestionTime


SQL Update query is used to change a record

An update example for a SQL Server database:

• Updates the Scores table• Sets each field equal to the parameter value passed• The Where clause is used to determine which record or records to update

Updating Records

UPDATE Scores SET StudentAnswer = {0}, Points = {1} WHERE ID = {2}


SQL Delete query is used to remove a record

A delete example for a SQL Server database:

• The Where clause determines the record or records to delete

What would happen without the Where clause?

Deleting Records

DELETE FROM Scores WHERE ID = {0}


Chapter Contents



Database CRUD



Retrieving Records





NuGet

NuGet is a technology to add functionality to the .NET Framework

Classes added as packages• Developed by Microsoft or others

We will use it to add the Entity Framework• Functionality for database access


Adding Entity Framework

Entity Framework is added to a project as a NuGet package• Multiple files and references are added at the same time

Steps1. Select Tools | Library Package Manager | Manage NuGet Packages for Solution2. Select EntityFramework

and click Install3. Select the projects to use

EF in4. Accept the license

agreement


Use the Entity Framework DbContext class to connect to SQL Server• Add an Imports (using) statement to System.Data.Entity• Create the DbContext class passing a connection string in the constructor• Return the Database property


Accessing a SQL Server Database

Public Shared ReadOnly Property FlashCardsDatabase As DatabaseGet

Dim connection As String = "Data Source=(LocalDB)\v11.0;AttachDbFilename=…”

Return New DbContext(connection).DatabaseEnd Get

End Propertypublic static Database FlashCardsDatabase{

get{

string connection = @"Data Source=(LocalDB)\v11.0;AttachDbFilename=…";

return new DbContext(connection).Database;}

}In C#, the @ sign is required here, so the “\” characters in the connection string are treated literally as “\” characters


Server Explorer automatically generates connection strings• Select the database from the Data Connections branch of Server Explorer• Can then copy and paste the connection string from the Properties window

Generating a Connection String


Use the ExecuteSqlCommand()method of the Database class

1. Define the SQL statement as a string• Use {#} placeholders to embed parameters into the query

2. Call the ExecuteSqlCommand() method passing the SQL statement followed by values for the required parameters

Running a Query

Insert, Update, and Delete queries are all run the same way.Only the queries and the parameters are different.


Visual Basic code:

Running a Query

Public Shared Sub SaveFlashCard(flashCard As FlashCardsGame, studentAnswer As Double, points As Integer)

Dim sql As Stringsql = "INSERT INTO Scores (UserName, QuestionTime, Equation,

CorrectAnswer, StudentAnswer, Points) VALUES ({0}, {1}, {2}, {3}, {4}, {5})”

FlashCardsDatabase.ExecuteSqlCommand(sql, flashCard.User, DateTime.Now, flashCard.BuildEquation(), flashCard.CalculateCorrectAnswer(), studentAnswer, points)

End Sub


C# code:

Running a Query

public static void SaveFlashCard(FlashCardsGame flashCard, doublestudentAnswer, int points)

{string sql;sql = "INSERT INTO Scores (UserName, QuestionTime, Equation,

CorrectAnswer, StudentAnswer, Points) VALUES ({0}, {1}, {2}, {3}, {4}, {5})";

FlashCardsDatabase.ExecuteSqlCommand(sql, flashCard.User, DateTime.Now, flashCard.BuildEquation(), flashCard.CalculateCorrectAnswer(), studentAnswer, points);

}


Methods can be declared as Shared in VB or static in C#• These methods can then be called without creating an instance of the class• Just specify the class name and and the method name

– Console.ReadLine() is an example of a static method

VB code:

C# code:

Shared (static) Methods

FlashCardsDataAccess.SaveFlashCard(game, answer, 10);

FlashCardsDataAccess.SaveFlashCard(game, answer, 10)


Chapter Contents



Database CRUD


Hands-On Exercise 6.2 Retrieving Records






In your Exercise Manual, please refer to Hands-On Exercise 6.2: Saving Data in the Database


Chapter Contents



Database CRUD



Retrieving Records Hands-On Exercise 6.3




Use the SqlQuery() method of the Database class• Pass a SQL Select statement and required parameters as arguments• Returns a collection that contains the query results

Needs a class that will contain the results of the query• Properties required for each field being returned by the Select statement• Entity Framework will automatically create an instance for each record returned• Class properties will automatically be set

Use a For-Each loop to loop through the returned collection

Executing a Select Query


Visual Basic code:


Public Shared Function GetLifeTimeStatistics(username As String) As String

Dim sql As StringDim questions, correct, points As Integer

sql = "SELECT CorrectAnswer, StudentAnswer, Points FROM Scores WHERE UserName = {0}"

Dim scores = FlashCardsDatabase.SqlQuery(Of Score)(sql, username)

For Each score In scoresquestions += 1If score.CorrectAnswer = score.StudentAnswer Then

correct += 1End Ifpoints += score.Points

Next

Return String.Format _("All time, you have {0} correct out of {1} questions for {2} points." _, correct, questions, points)

End Function


C# code:


public static string GetLifeTimeStatistics(string username){

string sql;int questions = 0;int correct = 0;int points = 0;

sql = "Select CorrectAnswer, StudentAnswer, Points FROM Scores WHERE UserName = {0}";

var scores = FlashCardsDatabase.SqlQuery<Score>(sql, username);

foreach (var score in scores){

questions += 1;if (score.CorrectAnswer == score.StudentAnswer)

correct += 1;points += score.Points;

}return String.Format(

"All time, you have {0} correct out of {1} questions for {2} points.”, correct, questions, points);

}


A class is required to hold the results of a select query• Must contain a property for each field being returned

VB code:

C# code:

Class to Hold the Query Result

Public Class ScorePublic Property CorrectAnswer As DoublePublic Property StudentAnswer As DoublePublic Property Points As Integer

End Class

public class Score{

public double CorrectAnswer { get; set; }public double StudentAnswer { get; set; }public int Points { get; set; }

}


Easy way to loop through each item in a collection of item• Create a variable to represent each item• Specify the collection to loop through

VB and C# code:

For-Each Loop

For Each score In scoresquestions += 1If score.CorrectAnswer = score.StudentAnswer Then

correct += 1End Ifpoints += score.Points

Next

foreach (var score in scores){

questions += 1;if (score.CorrectAnswer == score.StudentAnswer)

correct += 1;points += score.Points;

}


Chapter Contents



Database CRUD



Retrieving Records

Hands-On Exercise 6.3 Data Binding With ASP.NET




In your Exercise Manual, please refer to Hands-On Exercise 6.3: Retrieving Database Data


Chapter Contents



Database CRUD



Retrieving Records


Data Binding With ASP.NET Hands-On Exercise 6.4


We delivered our Flash Cards application with the database and the lifetime scores, and it was exactly what they wanted

Now they want a student history page that shows all the flash cards they’ve ever answered



Data-Bound Controls

ASP.NET includes a number of controls that automate the display of database data

GridView is used to display data in an HTML table• Allows sorting, selecting, and editing of the data

FormView and DetailsView controls are used to display data one record at a time• Support paging, editing, inserting, and deleting

records

Repeater control allows any HTML content to be “repeated” for each row in a data source• Similar to a mail-merge in Word, but for HTML


All data-bound controls are used in a similar way• Can be configured using a wizard in the Visual Studio designer• Or can be configured in the ASP.NET source code directly

Each control is bound to a data source• Data sources retrieve the underlying data• The control then formats that data on the page

Configuring Data-Bound Controls


There are a number of different data source controls that can supply data to the controls• SQLDataSource is used to connect to any modern relational database• ObjectDataSource can return data from any function call

– Can also specify functions used to update data• XMLDataSource is used to display data from an XML file or web service• There are other data sources as well

Each data source works in a similar way• Every data-bound control

supports every data source

Data Sources

XML = extensible markup language


The case study uses SQLDataSource

1. Select the connection string

2. Save the connection string to the Web.config file

3. Select the table and fields to retrieve

4. Add Where clause to filter the data

Configure Data Source Wizard


Once the data source is configured, the grid displays each column• Click Edit Columns to specify formatting options• Check Enable Paging to divide results into multiple smaller pages of data• Check Enable Sorting to allow records to be sorted by column

Customizing the DataGrid Control


ASP.NET Source Code

<asp:HiddenField ID="username" runat="server" />

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"DataSourceID="HistoryDataSource" AllowPaging="True">

<Columns><asp:BoundField DataField="QuestionTime" HeaderText="QuestionTime" /><asp:BoundField DataField="Equation" HeaderText="Equation" /><asp:BoundField DataField="CorrectAnswer" HeaderText="CorrectAnswer" /><asp:BoundField DataField="StudentAnswer" HeaderText="StudentAnswer" /><asp:BoundField DataField="Points" HeaderText="Points” />

</Columns></asp:GridView>

<asp:SqlDataSource ID="HistoryDataSource" runat="server"ConnectionString="<%$ ConnectionStrings:ConnectionString %>”

SelectCommand="SELECT [QuestionTime], [Equation], [CorrectAnswer], [StudentAnswer], [Points] FROM [Scores] WHERE ([Username] = @Username) ORDER BY [QuestionTime] DESC">

<SelectParameters><asp:ControlParameter ControlID="username" Name="Username”

PropertyName="Value" Type="String" /></SelectParameters>

</asp:SqlDataSource>


Chapter Contents



Database CRUD



Retrieving Records






In your Exercise Manual, please refer to Hands-On Exercise 6.4: Data Binding With ASP.NET


You are now able to • Program a database application in .NET

You have Created a SQL Server database Written SQL queries to create, retrieve, update, and delete database data Executed SQL queries using Entity Framework code Automated the display of data on a web page using ASP.NET data binding

Chapter Summary


What do relational databases consist of?

What are the four types of queries used by application developers?

What tool in Visual Studio is used to access SQL Server databases?

What are the steps to executing a query in a .NET program?



Suppose you have a table called Users with the fields ID, Username, and Password, where ID is the primary key. Write valid Insert, Update, and Delete queries below:



Designing SQL Server databases, see• Course 2107, SQL Server® 2012 Introduction


®

2107

Deployment

Chapter 7


After completing this chapter, you will be able to • Deploy a .NET application

To accomplish this, you will see how to Use ClickOnce deployment to install the Flash Cards Windows version Publish the Flash Cards ASP.NET application to the web

Chapter Objectives


Chapter Contents

Prerequisites Deploying Windows Applications

With ClickOnce

Publishing Web Applications


Prior to .NET, Windows deployment required complex setup programs• Changes were made to the Windows Registry• Because components (.dlls) were shared by applications, installing a new

application sometimes broke an old application

.NET deployment has been vastly simplified• Install the .NET Framework in the target computer• Copy the application’s files onto that machine• Test!

Web and Windows deployment are only slightly different• Web applications need to be on a machine with IIS installed• A virtual directory needs to be created on the server to put the web application

in

Deploying .NET Applications


Download and install from Microsoft’s website• dotnetfx.exe is the program that needs to be downloaded and run• Make sure to get the correct version

– Version 1.1 if using Visual Studio 2003– Version 2.0 if using Visual Studio 2005– Version 3.5 if using Visual Studio 2008– Version 4.0 if using Visual Studio 2010– Version 4.5 if using Visual Studio 2012– Version 4.5.1 if using Visual Studio 2013

See Microsoft’s website for links and information• The .NET Framework home page:http://msdn.microsoft.com/netframework/

Important if deploying a web application!• IIS must be installed and running before installing the .NET Framework• Test it by opening a browser and typing:http://localhost

Installing the .NET Framework


Before deployment, change the build from Debug to Release• Optimizes the build for performance• Eliminates breakpoints• Removes any output to the debug window

Select the Build | Configuration Manager menu• Or just select Release from the Configuration Manager drop-down on the

Visual Studio toolbar

Configuring a Release Build


Every project is compiled to target a .NET Framework version• Can set this under Project Properties

The target framework must be installed on the target machine• Can specify an earlier version, but then newer .NET features are not available

Target Framework Version


Chapter Contents

Prerequisites

Deploying Windows Applications With ClickOnce



Publishing an application with ClickOnce• Copies the application and its required files to a virtual directory or folder• Automatically checks for and installs .NET on the user’s machine• Can automatically check for new versions of the application

Two types of ClickOnce deployments:• Launched applications• Installed applications

ClickOnce Deployment


Launched applications are available only over the web• Must click a hyperlink to the ClickOnce deployment manifest• To update a program, just re-publish it

– Most up-to-date version of the program is always run• Application cannot be run if the user is offline

Installed applications• The user must be online to do the initial install of the application• The application is downloaded and a Start menu icon is created

– The application now works on- or offline• Can configure the application to check for updates when it is run

Launched vs. Installed Applications


Done from the Publish tab of the project properties window• Publish location can be a web server, FTP server, or just a folder location• Specify whether to use a launched or installed application• Specify prerequisites and how to handle updates• Specify the version number

Configuring ClickOnce Deployment

FTP = File Transfer Protocol


Prerequisites are components required by the application• The correct version of the .NET Framework is always a prerequisite• May also include SQL Server Express, the Windows Installer, etc.• Prerequisites can be downloaded from the vendor’s website

Prerequisites


The deployment can be set up to check for new versions• Either before or after the application starts• The program will automatically look for new versions when started• Users will be prompted to install the new version

Specifying a minimum version number will force users to update

Updates


ClickOnce creates a setup program and a deployment manifest• Deploy to a web server, and then provide users a hyperlink to the manifest

If it is an installed application, a Start menu icon will be created• Users can remove the program from the Control Panel• The program will check for updates every time it is started

Deployed Files


Chapter Contents

Prerequisites

Deploying Windows Applications With ClickOnce



An ASP.NET application must be deployed to a server• Server requires Internet Information Services (IIS) to be installed

– Done differently depending on the version of Windows• ASP.NET must be installed on the server

as well

Multiple versions of ASP.NET can be installed on the same server• Each application must be configured to use

the correct version

Configuring IIS for ASP.NET Hosting


Every ASP.NET application runs in an application pool• One application pool is assigned as the default• Each application pool uses a .NET Framework version• Can add any number of application pools

Application pools also are assigned an identity• This is the account that an ASP.NET application will run under• The application cannot do anything not allowed by that account

Application Pools


An ASP.NET application will be assigned to the default application pool• Can be changed by going to that web application’s advanced settings

An ASP.NET application should have an application pool that• Uses the correct .NET Framework version• Has an identity that has

the rights required by the application

Assigning Application Pools to ASP.NET Websites

ASP.NET 3 and 3.5 applications use .NET 2 application pools.

ASP.NET 4.5 applications use .NET 4 application pools.


Can create publishing profiles that control how a website is deployed• Right-click the ASP.NET project and select Publish

Configure• Where the web application is deployed• Production database connection strings• Can deploy databases to a target SQL Server

Web Publishing


In the Connection tab, specify the target web server• Service URL is the domain name or IP address of the server• Site application is the target web application name• Web deployment must be configured on this server by the administrator

If web deployment is not enabled, select Web Deployment Package as the publish method• This will create a .zip file

with the application• This can then be imported

manually by the web serveradministrator

Specifying Web Server Location


Configure database settings on the Settings tab• Specify connection strings to production server• The Web.config file will be updated automatically on the web server• “Update database” checkbox will add databases to the database server

Database Settings


Click the Publish button to deploy the application• Web application will be created or updated on the web server• Databases will be deployed• Web.config file will be updated

Publishing the Application


The database connection string was hard-coded into the application• Once the site is deployed, this connection string will be different• The solution is to read the connection string from the config file at runtime

Steps:• Set a reference to the System.Configuration library• Use the ConfigurationManager class to read the connection string

VB code:

C# code:

Reading Connection Strings From the Web.Config File

Dim connection As String = ConfigurationManager.ConnectionStrings("FlashCardsConnectionString").ConnectionString

Return New DbContext(connection).Database

string connection = ConfigurationManager.ConnectionStrings["FlashCardsConnectionString"].ConnectionString;

return new DbContext(connection).Database;


You are now able to • Deploy a .NET application

You have seen how to Use ClickOnce deployment to install the Flash Cards Windows version Publish the Flash Cards ASP.NET application to the web

Chapter Summary

Course Summary

Chapter 8


We deployed our Flash Cards application. But then kids starting using it and, based on their feedback, we have the following additional requirements:1. The students said there should be levels. The questions should start easy

and get harder and they should get more points at higher levels2. There should be a High Scores page3. They want avatars (pictures that express their mood) attached to their

accounts4. They didn’t like how it looked. There needs to be a better theme and it

should be customizable by the student

This is your homework• Everything required to implement these features, we have learned this week



Go to www.bbqmath.com to see a finished version of the case study• Completed source code is also available

Course 502 Case Study Online


Please visit our .NET blog• http://dotnet.learningtree.com

Learning Tree International’s .NET Blog


To learn more about analysis, OO design, and testing, see• Course 933, Agile Software Development and Modeling

To learn more about ASP.NET web development, see• Course 2621, Building ASP.NET Web Applications

To learn more about a .NET language, see• Course 419, C# Programming• Course 503, Visual Basic® Programming for .NET

Where to Go From Here

®

OO = object-oriented

9332621419503


In this course, you have

Designed and programmed applications using Microsoft .NET and Visual Studio

Learned the syntax of the VB and C# programming languages

Written a .NET Windows Forms application

Coded for reuse using object orientation, inheritance, and class libraries

Created and programmed an ASP.NET website

Allowed users to log in and create accounts using Web Forms authentication

Created a SQL Server database

Saved and accessed database data using .NET

Deployed .NET Windows and web applications

Course Summary

Answers to Review Questions and Glossary

Appendix A

2© Learning Tree International, Inc. All rights reserved. Not to be reproduced without prior written consent. A-

• What are the different types of applications that can be created with .NET?

____________________________________________________________

• What is a .NET program’s entry point?

____________________________________________________________

• Which are the two most common .NET languages? Which is better?

____________________________________________________________

• What tool in Visual Studio is used to manage projects?

____________________________________________________________

• What is a statement?

____________________________________________________________


Windows Forms, ASP.NET Web, Console applications, and others

A void function or subroutine called Main()

Visual Basic and C#. Both offer the same functionality; only the syntax is different.

Solution Explorer

A line of code


• Code in .NET must be written inside a:

____________________________________________________________

• Name three things that might be in a class:

____________________________________________________________

• What must be specified when declaring a variable?

____________________________________________________________

Properties provide access to what within a class?

____________________________________________________________

Define a method:

____________________________________________________________


A class

Fields (variables), Methods (functions), Properties (methods disguised as fields)

Name, data type, and visibility

The data required by a class

A method is a named block of code that performs a series of statements (a function).


• What are the two types of numbers?

____________________________________________________________

• How would one decide whether to declare a variable as Integer or Long?

____________________________________________________________

• What does it mean to say that .NET is a type-safe environment?

____________________________________________________________

• How could a String be converted to an Integer?

____________________________________________________________

• What is implicit type conversion?

____________________________________________________________


Integer and real numbers

Based on how large (or small) the variable could be

Only a valid value can be assigned to a variable based on its declared type

i = Integer.Parse("100") or Integer.TryParse("100", i)

An automatic type conversion that the system will do when there is no chance for loss of data. For example, when converting an Integer into a Double.


What constructs can be used for a decision-making statement?

________________________________________________________________

What are the two types of loops?

________________________________________________________________

When should a Try-Catch error handler be used?

________________________________________________________________

Rewrite the following using a Select-Case or switch statement:


Dim pet as StringIf pet = "Dog" then

Feed("Bone")ElseIf pet = "Cat" then

Feed("Catsup")ElseIf pet = "Frog" then

Feed("ToCat")Else

Feed("Steak")End If

If or Select-Case (switch)

For-Next and Do-While loops

In exceptional circumstances; i.e., things that are beyond a programmer’s control

Select Case petCase "Dog"

Feed("Bone")Case "Cat"

Feed("Catsup")Case "Frog"

Feed("ToCat")Case Else

Feed("Steak")End Select


• What does a Windows application consist of?

____________________________________________________________

• What method is used to display a form on the screen?

____________________________________________________________

• What are some of the standard Windows controls?

____________________________________________________________

• What is the difference between an event and an event handler?

____________________________________________________________

• What does it mean to display a form modally? How is this done?

____________________________________________________________


A collection of forms, each of which contains a collection of controls

Show()

Label, TextBox, Button, Checkbox, RadioButton, ComboBox, ListBox, etc.

An event is a message sent from a class; a handler is a function that runs in response

Code execution stops until a modal form is closed. Use the ShowDialog()method to display a form modally


• Define the Single Responsibility Principle:

______________________________________________________________

• Define a constructor:

______________________________________________________________

• Give two reasons to use inheritance:

_______________________________________________________________

_______________________________________________________________

• List some advantages of class libraries:

_______________________________________________________________


A class should have only one reason to change. It should do one complete job.

A function that runs automatically when a class is created

1. Reduce code duplication

2. Reduce complexity

Reusability, better organization, easier to divide the work on large projects


• In web applications, requests are made via which protocol?

_______________________________________________________________

• What language is used to display data in a browser?

_______________________________________________________________

• What HTML tag is used to allow a user to send data to a web server?

_______________________________________________________________

• What would be the syntax for a link to Microsoft’s website?

_______________________________________________________________


HTTP over TCP/IP

HTML

<Form></Form>

<a href="http://www.microsoft.com">Microsoft</a>


• In .NET, what technology is used to create web applications?

_______________________________________________________________

• What property of the page object determines if the form was submitted?

_______________________________________________________________

• What ASP.NET object is used to create user variables?

_______________________________________________________________

• To force all users of a website to create an account, what access rule would be written?

_______________________________________________________________


ASP.NET

IsPostback

Session

<deny users="?" />


• What do relational databases consist of?

_____________________________________________________________

• What are the four types of queries used by application developers?

_____________________________________________________________

• What tool in Visual Studio is used to access SQL Server databases?

_____________________________________________________________

• What are the steps to executing a query in a .NET program?

_____________________________________________________________


Tables, indexes, relationships

Select, Insert, Update, Delete

Server Explorer

1. Create a Entity Database object, using an appropriate connection string2. Specify a SQL query (including parameters) to run3. Use the ExecuteSQLCommand method of the DbContext.Database object,

including the SQL text and the required parameters


• Suppose you have a table called Users with the fields ID, Username, and Password, where ID is the primary key. Write valid Insert, Update, and Delete queries below:

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________


Insert Into Users (ID, Username, Password) Values (@ID, @Username,@Password)

Update Users Set Username = @UserName, Password = @Password WhereID = @ID

Delete From Users Where ID = @ID


Abstract method: A method definition inside a base class; there is no real implementation programmed, and it forces the derived class to include the method

Array: A variable that can contain multiple values

Class: The primary container for code in a .NET program, defined using the Class keyword; classes contain fields, methods, properties, events, and constructors

Constructor: A function that runs automatically when a class is created

Dialog form: A form that is used to query the user for information; typically shown on the screen modally

Event: A message sent from controls or other objects; some action causes an event to be raised; programmer can choose to respond to the event or not

Event handler: A function that runs in response to an event being raised

Glossary


Exception: A message sent from a method in response to some invalid circumstance; exceptions must be caught, or the program will crash

Field: A variable declared directly inside a class, not inside a function

Function: A named block of code that performs a series of statements

HTML: (hypertext markup language) A text-based markup language used to format data in a browser

Index: Consists of one or more fields sorted alphabetically for each record; includes the position in the file for each record; indexes allow records to be found quickly

Inheritance: Allows a class to reuse and extend functionality of another; the base class provides the reusable behavior; the derived class can add new behaviors or change the existing behaviors

Integration tests: A higher-level test that proves that multiple units or classes work well together

Glossary


Loop: A series of statements that needs to be repeated a number of times

Method: A function defined inside a class

Object: An instance of a class in memory, hence the term object-oriented programming

Property: A method disguised as a field; when fully implemented, contains two parts: the Get clause is used to return a value; the Setclause is used to change the value of an underlying field

Regression tests: Tests that prove that changes to code don’t break existing functionality

Relationship: Specifies how the records in the tables of a relational database are linked; one-to-many relationships are the most common, where the primary key of one table has a link to a foreign key in another table

Glossary


Scope: Determines when a variable or function is loaded into memory; a variable or function is available as long as it is in memory; a variable’s lifetime ends when it goes out of scope, and it is removed from memory

Single Responsibility Principle: A class should have only one reason to change; it should do one job completely

Statement: A line of code

SQL: The standard language used by all databases, for all modifications

Unit tests: Low-level tests that prove that the functionality provided by “units” of code works correctly

Variable: A named location in memory used to store, retrieve, and change data

Virtual directory: A folder that appears to be below the web server’s root, but may be located at any physical location

Glossary


Virtual method: A method that is programmed in the base class but can be changed in the derived class if necessary

Visibility: Determines whether a variable or function can be used outside its class; a variable’s or function’s visibility can be public or private

Glossary

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