learning by sample gdi+ -gradient

w w w . B u k a n S e m b a r a n g . I n f o © 2 0 1 0

Page 0

GDI+ : Gradient 2010


GDI+ : Gradient

Learning By Sample Series


Page 1


Foreword

Learning By Sample ?

So, why should I made this tutorial freely accessed by everyone ? Well, surely I

am just nobody, I also just another ordinary person with ordinary knowledge. However,

I always feel that some persons in the internet giving away their tutorial for free and I

feel being helped by them. Then, I remember one of my senior wisdom words : “If you

want to be given more, then start to give more”. And of course, I really believe those

words, since that I already proof it to be right all the time.

Also, I’m not an English native speaker, however, I just try to improve my

English in any other way, especially in written format. Thus, I think writing is the best

practice to improve my English freely. However, you will find many grammatical errors

in my tutorial, so please send me comments and also suggestion to improve it.

Then, why the format using Learning By Sample series ? Is it really different with

other tutorials out there ? Ehm, I already wrote three books (in Indonesian) using this

kind of format, and many readers already contact me about how this format really help

them to learn from the scratch. So, why in the world I’m not re-create it in English

format, right ? Eventhough actually, it is similar with Hands On Lab series which

already famous in Microsoft site previously.

All of my lesson also being designed as short samples and short time exercise.

Thus, I hope that each of tutorial series would take only at least 10-15 minutes

maximum to learn. Why keep it short ? Because many beginner (and even expert) will

find boring whenever they must keep studying more than 15 minutes (but you will

never get bored when you online in such time right ?).


Page 2


Another reason is just because many of samples in this series come up from my

lecturing task exercise. So, I just try to compile all my lab exercises in order to keep it

tidy and also reusable for my students. That’s why you will find many unsorted course

material inside these series, however, just take a seat and enjoy the ride !

Requirements

In this series, I try to give simple example about GDI+. So what is GDI+ anyway ?

GDI+ or GraphicsDrawing Interface is merely part of .NET Framework which entirely

purposed in manipulating graphics. However I’m not going to make you understand

complex theory about this class. I just try to make you understand it in very simple and

stupid way.

All of my samples in this series use Visual Web Developer 2010 Express edition

however you can also do it all using Visual Studio. If you really want to follow this

series, then you should aware that basic programming knowledge is needed. You

should also familiar with ASP .NET especially for version 3.5 above.

FYI, I’m a VB guy, so please don’t complaint if I use VB entirely in this series. But

nowadays, there’s no such useful things if we argue about language differences,

because I just try to share something that I know. So, if you don’t like VB and want to

have another tutorial with your own favourit language, then I’d be happy to read it.

Now, let’s get started…….


Page 3


Let’s Get Started

1. First, ensure that you already open Visual Web Developer 2010 Express Edition

2. Create a newly blank website and give it a name

3. Now, let’s create a new blank web page


Page 4


4. In newly created web page, insert new table which has 3 rows and 2 columns, by

clicking menu Table � Insert Table and in available dialog box set its rows and

columns value :

5. Then type descriptive text in first and second row at first column


Page 5


6. Later put two DropDownList in each rows at second column :

7. Next, put a Button in last row at first column and set its Text property just like this

following picture :

8. Last step in design mode is placing an Image control just right after Button :


Page 6


9. Double click at any empty space in Design mode and we should be redirect in to

Page_Load event, and type this codes :

a. First thing first, in this part of code we declare Color enumeration. As you

should know that there are KnownColor enumeration in Color classes at .NET

Framework.

b. Then why we should start it at number 27 ? It just because the first color

until color number 27 merely contains known color from client desktop

theme. It also happen in last 8 known color, thus we do the looping from 27

until last 8 only.

c. And the rest is easy, we just put all the color’s array into available

DropDownList


Page 7


10. Now let’s turn again into Code Editor by double clicking the only available Button

and start typing this lines of code :

11. Some typo errors shown ? Don’t worry, just add this line at top of Code Editor :

12. Want some explanations for what the Button do ? Here it go :

a. First, we create the “canvas” for our next gradient brush

b. Next we create the “core” gradient brush with Horizontal Linear mode, you

can also modify it using other mode such as Diagonal or Vertical


Page 8


c. In following part, we create a virtual rectangle to hold the gradient sample

d. Afterward, just save it in temporary image file and display it in Image control

e. Of course, never forget to dispose all the object

13. Okay then, let’s execute this web page and see the result :


Page 9


14. What do you think ? Too easy ? Well, have fun to try it and we will create another

simple and astonishing sample in next chapter…..

learning by sample gdi+ -gradient

Education

sample series gdi

tutorial series

lab series

english format

known color

created web page

color classes

short samples