Build Your Own ASP.NET 2.0 Web Site Using C# & VB, Second Edition

But what does Partial mean? A new feature in .NET 2.0, partial classes allow

a class to be spread over multiple files. ASP.NET 2.0 uses this feature to make

programmers’ lives easier. We write one part of the class in the code-behind file,

and ASP.NET generates the other part of the class for us, adding the object de-

clarations for all the user interface elements.

Take a look at the Click subroutine, though which we access the messageLabel

object without defining it anywhere in the code:

Visual Basic File: HelloCodeBehind.vb (excerpt)

Sub Click(s As Object, e As EventArgs)

messageLabel.Text = "Hello World"

End Sub

That’s pretty handy! However, don’t be fooled into thinking that you can use

objects that haven’t been declared—the messageLabel object has been declared

in another partial class file that the ASP.NET runtime generates for us. The file

contains declarations for all the controls referenced in HelloCodeBehind.aspx.

As I hope you can see, code-behind files are easy to work with, and they can make

managing and using our pages much more straightforward than keeping your

code in code declaration blocks. You’ll find yourself using code-behind files in

most of the real-world projects that you build, but for simplicity’s sake, we’ll stick

with code declaration blocks for one more chapter.

Summary

Phew! We’ve covered quite a few concepts over the course of this chapter. Don’t

worry—with a little practice, these concepts will become second nature to you.

I hope you leave this chapter with a basic understanding of programming concepts

as they relate to the ASP.NET web developer.

The next chapter will begin to put all the concepts that we’ve covered so far into

practice. We’ll begin by working with HTML Controls, Web Forms, and Web

Controls, before launching into our first hands-on project!

92

Chapter 3: VB and C# Programming Basics