c sharp programming slides 01-fp2005-ver1.0

8/9/2019 C Sharp Programming SLIDES 01-FP2005-Ver1.0

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C Sharp Programming Day 1


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Copyright 2005,Infosys Technologies Ltd

ER/CORP/CRS/LA30FC/003

Version no: 2.0

2

Course Objectives

To introduce the participants to C# programming and object oriented features

of C#

To understand the component oriented features of C# like indexers, properties,

attributes and illustrate their usage in programs

To introduce development of Assembly

To introduce Windows programming and delegate based event handling in C#

To understand Exception handling techniques in C# To introduce Multithreading in C#

To introduce to Reflection

To introduce File Handling in C#

To introduce Parsing

To introduce concept of Remoting through C# programs To introduce Windows Services

To introduce Application Deployment


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Version no: 2.0

3

Day Wise Plan

Day1

Recap of OO

- Data Types

- Class & Object

- Inheritance

- Namespace

- Structure

Day 2

Interface

Assembly

Property Indexer

Collection

Preprocessor Directives


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Version no: 2.0

4

Day Wise Plan

Day 3

GUI

Delegates

Unsafe Code

Exception Handling

Debugging

Day 4

Threading

Reflection

Serialization

File Handling

Day 5

Parsing

Remoting

Windows Services

Deployment

Day 6 and Day 7 - Project


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Version no: 2.06

Session Plan

Recap of OO

Classes and Objects

Basic Data Types and Control structures,

Data Members and Methods of a Class (Creation of objects)

Constructors

Destructors

Garbage Collection

Static

Command Line Arguments

Inheritance

Overloading and Overriding

Abstract and Sealed Namespaces

Structures


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Version no: 2.07

Recap of Object Oriented Concepts

Classes

templates used for defining new types.

Contains attributes and behavior

Instance of a class is called an Object


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Version no: 2.0

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Recap of Object Oriented Concepts

Encapsulation

Mechanism that binds together code and the data it manipulates in a class

Data members are made private and are prevented from being accessed

by outside classes thus achieves Data Hiding

Inheritance

Process by which one object can acquire the properties of another object. Supports hierarchical classification

Polymorphism

-Ability of objects to respond in their own unique way to the same message


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Version no: 2.0

9

Structure of a C# program

using System;

namespace InsideCSharp

{

class FirstProgram

{

public static void Main()

{

Console.WriteLine(Hello World);

}

}

}


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Version no: 2.010

Structure of a C# program

The extension of a C# program is cs There is no restriction on the filename unless it follows the naming convention

of the OS

Every statement in C# ends with ;

Main is the starting point of execution of a C# program

{ } describes a block of code

Main function must be written inside the class


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Version no: 2.011

Data Types

Value Types Reference Types

Value types include simple types like

char, int, and float, enum types, and

struct types

Reference types include class types,

interface types, delegate types, and

array types

Variable holds the actual value Variable holds memory location

Allocated on stack Allocated on heap

Assignment of one value type to

another copies the value

Assignment of one reference type to

another copies the reference


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Version no: 2.012

Data Types Value Types

Data Types

IntegerFloating

PointCharacter Boolean

byte

sbyte

short

ushort

int

float

double

Char bool

uint

long

ulong

decimal


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Version no: 2.013

Data Types Value Types

Data Type Description Range

bool Represents true/false

byte 8 bit unsigned integer 0 to 255

sbyte 8 bit signed integer -128 to 127

short Short integer 16 bits -32,768 to +32,767

ushort Unsigned short integer 16 bits 0 to 65535

int Integer 32 bits -2,147,483,648 to 2,147,483,647

uint Unsigned integer 32

bits 0 to4,294

,967,

295

long Long integer 64 bits -9,223,372,036,854,775,808 to9,223,372,036,854,775,807

ulong Unsigned long integer 64 bits 0 to 18,446,744,073,709,551,615

float Single precision floating point 32 bits 1.5E-45 to 3.4E+38

double Double precision floating point 64 bits 5E-324 to 1.7E+308

decimal Numeric type for financial calculations 128 bits (supportsupto 28 decimal places)

1E-28 to 7.9E+28

char Character 16 bit (uses Unicode)


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Version no: 2.014

Variables Value Types

Declaration syntax of a variable in C#:

Ex:

int iNum;

Initializing variables:

Ex:

int iNum = 10;

Variables in C# can be declared anywhere before referencing them.

The scope of the variable is from the declaration till the end of the block in whichit is declared.


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Version no: 2.015

What is the output of the following program?

using System;

class Test

{


{

int iNum = 10;

{int iNum = 100;

Console.WriteLine(iNum);

}


}}

ERROR

The variable iNumis still in

scope in the inner block


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Version no: 2.016

This slide has been intentionally left blank : Notes

Page Contd.


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Version no: 2.017

C# is a strongly typed language

Automatic conversions (or widening conversions) from one type to another

takes place if: the source and the destination types are compatible

the destination type is larger than the source type

Automatic conversions in C# does not happen that leads to data loss.

Explicit conversions require type casting.

int iVal = 1234;

long lVal = iVal;

double dVal = 34.23;

float fVal = dVal;

long lVal = 23456;

int iVal = (int) lVal;

This implicit conversion

does not lead to data loss

The above statement does not

compile as conversion from

double to float leads to data loss.

This is an example of

explicit conversion


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Version no: 2.018

Literals Value Types

Also called constants.

Integer literals can be of type int, uint, long or ulong depending on their value.

Ex:

12l or 12L is of long type

12ul or 12UL is of ulong type

12u of 12U is of unsigned integer type, uint

Floating point literals of type double

Ex:

12.3F or 12.3f is of type float

9.92M or 9.92m is of type decimal

Boolean literals

Ex:

bool b = true;


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Version no: 2.019

Types Boxing

Conversion of Value type to Reference Type

Allocates box, copies value into it Unboxing

Conversion of Reference Type back to Value Type

Checks type of box, copies value out

int iVal = 123;int iVal = 123;object oVal = iVal;object oVal = iVal;

int iValue = (int)oVal;int iValue = (int)oVal;

123123iVal

oVal

123123System.Int32System.Int32

123123iValue


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Version no: 2.020

Control Structures if statement

Requires a boolean expression

int iNum = 10;

if ((iNum % 2) == 0)

{Console.WriteLine("Even Number");

}

else

{Console.WriteLine("Odd Number");

}


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Version no: 2.021

Control Structure switch statement

No two case constants in the same switch can have identical values.

Fall through rule:

Statement sequence from one case cannot continue to next case.

Can be avoided by using the goto

Default statement cannot fall through

Empty cases can fall through.


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Version no: 2.022


What is the output of the following code snippet?

int iNum=2;

switch(iNum)

{

case 1:


case 2:


break;

}

compile error - control

cannot fall through from one

case to another


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Version no: 2.023


char cChoice='i';

switch(cChoice)

{

case 'a':

case 'e':

case 'i':

case 'o':

case 'u':

Console.WriteLine("Vowels");

break;

default:Console.WriteLine("Consonants");

break;

}

Vowels


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Version no: 2.024

Control Structures - loops

while loop:

while (condition)

{

statement/s ;

}

do-while loop:

do

{

statement/s;

}while(condition)

for loop:

for (initialization; condition; iteration)

{

statement/s;

}

break;

continue;


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Version no: 2.025

Types User defined types

Enumerations

Arrays

Class

Structure

Interface

Delegate


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Version no: 2.026

Enumerations

Enumeration is a set of named integer constants.

General form of an enumeration:

enum name { enumeration list }

The members of an enumeration are accessed through their type-name and

the dot operator.

The statement:

Produces an output:

green has a value : 1

enum eColors { red, green, blue};

Console.WriteLine (eColors.green + has a value : +

(int) eColors.green);


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Version no: 2.027

Enumerations

Consider:

enum eColors { red, green=10, blue} ;

What are the values of the members?

red 0

green 10blue 11


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Version no: 2.028

Arrays

Two ways of creating one dimensional array:

Two ways of initializing one dimensional array:

Two Dimensional array or rectangular array syntax:

int [] aiNum;

aiNum = new int[10]; int [] aiNum = new int[10];

int[] aiNum = {1,2,3};int [] aiNum;aiNum = new int[] {1,2,3};

int[,] aiNum = new int[10,20];


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Version no: 2.029


Page Contd.


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Version no: 2.030

Jagged Arrays

Are two dimensional arrays in which the number of elements in each row can

vary.

int[][] aiNum = new int[2][]; // array with 2 rows

aiNum[0] = new int[10]; // first row has 10 elements

aiNum[1] = new int[12]; // second row has 12 elements

Jagged Array


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Version no: 2.031

Types : Reference Type - Class Instantiated with new operator

It consists of members like

Constants, fields, methods, operators, constructors, destructors

Properties, indexers, events

Members can be

Instance members.

Static members.

class Employee{

int iEmpId;

float fSalary;

void findSalary ()

{

// statements to calculate the salary

}

}


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Version no: 2.032

Object

Steps to instantiate a class

Counter oCounterOne ;

oCounterOne = new Counter();

A reference oCounterOne to

the Counter class is created

.oCounterOne does notdefine Counter

The new operator dynamically allocates

memory for an object of type Counterand returns a reference to it.

Note: The difference between a simple variable and the

reference type variable is that, simple variable holds the value

where a reference type variable points to a value.

Object


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Version no: 2.033

Objects in memory

Objects can be created in one step.

Ex: Counter oCounterOne = new Counter();

Object of type Counter

Reference

Variable:oCounterOne


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Version no: 2.034

Object Reference Assignment

ocounterOne oCounterTwo

Statement: oCounterTwo = oCounterOne;

oCounterOne oCounterTwo

Consider: Counter oCounterOne, oCounterTwo;

Object Reference


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ER/CORP/CRS/LA30FC/003Version no: 2.0

35

Access Modifiers

Access modifiers specify who can use a type or a member

Access modifiers control encapsulation Class members can be public, private, protected, internal, or

protected internal

to T or types derived from Tprotected

within T onlyprivate

to T or types derived from T

or to types within Aprotected internal

to types within Ainternal

to everyonepublic

Then a member defined in type T and Program A

is accessible

If the access

modifier is


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Class - Fields

A field

is a member variable of a class holds data for a class .By default each object of a class has its own copy of every

field

Static fields are shared by multiple objects.

public float fSalary;


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Class Read only Fields

Read only fields are constants

A read only field cannot be modified once initialized. Are initialized in its declaration or in a constructor.

public class MyClass {public static readonly double dNum = Math.Sin(Math.PI);public readonly string sStrOne;

public MyClass(string sStr) { sStrOne = sStr; } }


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Class Methods

All the executable code of a class is in its methods

Constructors, destructors and operators are special types of methods Methods can have argument lists, statements, can return a value

By default, data is passed by value where a copy of the data is created and

passed to the method


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A complete class

///

/// This is a counter class to count///

class Counter

{

//Counter variable

private int iCount;

///

/// This method is used to increment the value of thecount.

///

public void increment()

{

iCount++;

}

}

Class comment

block

Method comment

block


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Methods - ref parameters

ref modifier:

The ref modifier causes arguments to be passed by reference The ref modifier has to be used in the method definition and the code that

calls it

Call statement:

void RefFunction(ref int iP)

{

iP++;

}

int iNu

m = 10;RefFunction(ref iNum);

// iNum is now 11


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Page Contd.


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Page Contd.


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Methods - out parameters

out modifier:

the out parameter is used in cases where you need to return a value from amethod, but not pass a value to the method.

use out parameter to return more than one value from the method.

out parameter will not have any initial values but must be assigned a value

before the method terminates.

Out Parameter


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Methods passing variable number of arguments

Methods can have a variable number of arguments, called a parameter array

params keyword declares parameter array This must be last argument of the method and there can be only one such

argument.

int Sum(params int[] aiArr) {

int iSum = 0;

foreach (int iNum in aiArr)

iSum += iNum;

return iSum;

}

int iTotal = Sum(13,87,34);Parameter


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this keyword

When a local variable of a method has the same name as that of the instance

variable, the local variable hides the instance variable. In such cases, "this" can be used to refer to the instance variables.

class Demo

{

int i; // instance variable

public void fun (int i)

{

i = 10; // the local variable is referred

this.i = i; // to refer to the instance variable, this

is used

}

}


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static

use static to define a member that is independent of any objects

static members can not be accessed using an object of a class. instead, theyare accessed using the syntax:

classname.staticmembername

when objects of a class containing static members are created, a copy of the

static members are not made

all the instances of the class share the same static variable

Restrictions on static methods:

(a) this cannot be used in static methods

(b) static methods can call only static methods - because instance

methods act on specific instances of the class but static methods do not.

(c) static methods can access static data directly.


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What is the output of the following code snippet?

using System;

class Test{


{

anotherMethod();

}void anotherMethod()

{

Console.WriteLine(Another Method);

}

}

Compilation error: a non

static method cannot be

called from a static method


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Method Overloading

Two or more methods within the same class can have same name, but the

parameters must vary. In general, the type or the number of parameters must differ.

The signature (name of the method and its parameter list) does not include a

params parameter if one is present. params does not participate in

overloading

Method Overload


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Constructor

Is special method that is called whenever an instance of the class is created.

It guarantees that the object will go through proper initialization before beingused.

It is without any return value.

It has same name as its class.

Access specifier must be public as constructors are called from outside the

class.

It can be overloaded.

Constru tor

Thi lid h b i t ti ll l ft bl k N t


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Page Contd.



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Page Contd.


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Static Constructors

used to initialize the static variables

access modifiers like public are not allowed on static constructors are called only once during the lifetime of the program

Static Co structor


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Destructors

A destructor is a method that is called when an instance goes out of scope

Used to clean up any resources Only classes can have destructors

~Employee()

{

// destruction code

}



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Page Contd.


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Garbage Collection

Automatic Memory Management Scheme

Garbage Collector always run in background of an application.


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Finalize

Finalize method is defined in Object class.

A finalizer executes when the object is destroyed.

In C# the declaration of the destructor is a short cut for the Finalize() method.


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Dispose

Free resources that need to be reclaimed as quickly as possible.

Explicitly called.

public void Dispose()

{

Console.WriteLine(Dispose());

}


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Operators - overview

C# provides a fixed set of operators, whose meaning is defined for the

predefined types Some operators can be overloaded (e.g. +)

Associativity

Assignment and ternary conditional operators are right-associative

Operations performed right to left

x = y = z evaluates as x = (y = z)

All other binary operators are left-associative Operations performed left to right

x + y + z evaluates as (x + y) + z

Use parentheses to control order


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class Car {

string vid;

public static bool operator ==(Car x, Car y) {return x.vid == y.vid;

}

}

Operator Overloading

Operator Overloading helps in creating user-defined operations

The method used to overload the operator must be a static method


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Operator Overloading

+ - ! ~

true false ++ --

Overloadable unary operators

Overloadable binary operators

+ - * / ! ~

% & | ^ == !=

> < > =

Oper t r Over


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Inheritance

Using inheritance, you can create a general class that defines a common set of

attributes and behaviors for a set of related items. A derived class is a specialized version of the base class and inherits all the

fields, properties, operators and indexers defined by base class

Protected members are private to the class but can be inherited and accessed

by the derived class

The constructor of the base class can be called from the derived class using the

keyword base.

Inherit nce


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Hidden Names and Inheritance

using System;

class Parent

{protected int p;

public Parent()

{

p = 10;

}

}

class Child : Parent

{

int p;

public Child()

{

p = 100;

}

public void displayParent()

{

Console.WriteLine(p);

}

}

class InheritanceTest

{public static void Main()

{

Child c = new Child();

c.displayParent();

}

}What does the statement

c.displayParent() display?

The child class member p hides the member p

of the parent class.

To access the member p of the Parent class,

use the syntax: base.member.

Refer to notes page for the above modified

program



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Page Contd.

Base class reference can refer to a derived class


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Base class reference can refer to a derived class

object A derived class object can be assigned to a base class reference

But the parent class reference cannot access the members of the derived class

Base Class

Reference


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Method Overriding and Virtual Methods

Method of a derived class can give another implementation to a method of the

base class Method of the base class must be marked virtual

Method of the derived class must be marked override

class Employee //base class

{

protected double basic;

protected double gross;

public virtual void CalcSal()

{

gross = basic + 0.5*basic;

}

}

class Manager : Employee

{

protected double allow;

public override void

CalcSal()

{

gross = basic +

0.5*basic + allow;

}

}



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Page Contd.


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Copyright 2005,Infosys Technologies LtdER/CORP/CRS/LA30FC/003

Version no: 2.067

Sealed modifier : methods

Applied to methods:

Cannot be overridden

class class1

{public override sealed int F1()

{

.

}

}

class class2 : class1

{

public override int F1()

{

}}

ERROR


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Copyright 2005,Infosys Technologies Ltd ER/CORP/CRS/LA30FC/003Version no: 2.068

Sealed modifier : Class

Applied to class

Cannot be derived

sealed class class1

{} class class2 : class1

{

}

ERROR


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Version no: 2.069

Abstract modifier

Applied to methods:

Methods cannot have implementation in base class Must be implemented in derived class and marked override

The class containing at least one abstract method must be declared

abstract

//base class

abstract class Employee

{

protected double basic;

protected double gross;

public abstract void

CalcSal();

}

class Manager : Employee

{

protected double allow;

public override void

CalcSal()

{

gross = basic +0.5*basic + allow;

}

}


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Version no: 2.070

Abstract modifier - Demos

Abstr ct (class1.cs) Abstr ct

(Class2.cs)


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Version no: 2.071

Namespaces Namespaces provide a way to uniquely identify a type.

Provides logical organization of types.

Namespaces can span assemblies.

Can be nested.

The fully qualified name of a type includes all namespaces.

namespace N1 { // is referred to as N1

class C1 { // is referred to as N1.C1

class C2 { // is referred to as N1.C1.C2

}

}

namespace N2 { // is referred to as N1.N2

class C2 { // is referred to as N1.N2.C2

}

}

}

Fully Qualified

name

Namespa e

P d fi d T Obj


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Version no: 2.072

Predefined Types - Object

Root of object hierarchy

Storage (book keeping) overhead 0 bytes for value types

8 bytes for reference types

P d fi d T St i


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Version no: 2.073

Predefined Types - String

A sequence of characters

Strings are immutable (once created the value does not change) String is Reference type and string class in C# is an alias of System.String

class in the dot net framework

The following special syntax for string literals is allowed as they are built in

data types.

String s = I am a string;

C# Type System Type

String System.String

P d fi d T St i B ild


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Version no: 2.074

Predefined Types - StringBuilder

Every time some modifications are done to the string a new String object

needs to be created StringBuilder class can be used to modify string without creating a new string

Ex : StringBuilder str = new StringBuilder (hi);

Properties:

Length

Methods

Append()

Insert()

Remove()

Replace()

StringBuilder str = new StringBuilder (hi);

str.Append(how are you?)

str.Insert(6,How do you do?);

String Builder

C d Li A t


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Version no: 2.075

Command Line Arguments

Arguments can be passed to Main function at the command prompt from

where the program is invoked. Main function can return an integer .

Four forms of Main:


public static int Main()

public static void Main(string[] args)

public static int Main(string[] args)

Command Line

Arguments

St t


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Version no: 2.076

Structure

Is a generalization of a user-defined data type (UDT)-Value type.

Is created when you want a single variable to hold multiple types of relateddata.

Is declared by using the keyword struct.

Can also include methods as its members.

member access levels possible are only public, internal, private

Structure



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Version no: 2.077

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Page Contd.



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Version no: 2.078

y

Page Contd.

Str ct re and Class Similarities


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Version no: 2.079

Structure and Class - Similarities

Both can have members, including constructors, properties, constants, andevents.

Both can implement interfaces.

Both can have static constructors, with or without parameters.

Structure and Class Differences


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Version no: 2.0

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Structure and Class - Differences

Class Str ucture

A class is inheritable from other existing

classes.

A structure is not inheritable.

A class can have instance constructors

with or without parameters.

A structure can have instance

constructors only if they takeparameters.

A class is a reference type. A structure is a value type.

Summary


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Version no: 2.0

8

1

Summary

Recap of OO

Basic Data Types and Control Structures Structure

Classes and Objects

Garbage Collection

Static

Command Line Arguments Inheritance

Overloading and Overriding

Abstract and Sealed

Namespaces

Structures


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Thank You!

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