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

C# File: Hello.aspx (excerpt)

<%@ Page Language="C#" %>

In this case, the Page directive specifies the language that’s to be used for the

application logic by setting the Language attribute. The value provided for this

attribute, which appears in quotes, specifies that we’re using either VB or C#. A

whole range of different directives is available; we’ll see a few more later in this

chapter.

Unlike ASP, ASP.NET directives can appear anywhere on a page, but they’re

commonly included at its very beginning.

Code Declaration Blocks

In Chapter 3, we’ll talk about code-behind pages and how they let us separate

our application logic from an ASP.NET page’s HTML. However, if you’re not

working with code-behind pages, you must use code declaration blocks to contain

all the application logic of your ASP.NET page. This application logic defines

variables, subroutines, functions, and more. In our page, we’ve placed the code

inside <script> tags, like so:

Visual Basic

<script runat="server">

Sub mySub()

' Code here

End Sub

</script>

Here, the tags enclose VB code, but it could just as easily be C#:

C#

<script runat="server">

void mySub()

{

// Code here

}

</script>

Comments in VB and C# Code

Both of these code snippets contain comments—explanatory text that will be ig-

nored by ASP.NET, but which serves to describe to us how the code works.

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Code Declaration Blocks

In VB code, a single quote or apostrophe (') indicates that the remainder of the

line is to be ignored as a comment.

In C# code, two slashes (//) achieve the same end. C# code also lets us span a

comment over multiple lines if we begin it with /* and end it with */, as in this

example:

C#

<script runat="server">

void mySub()

{

/* Multi-line

comment */

}

</script>

Before .NET emerged, ASP also supported such script tags using a runat="serv-

er" attribute. However, they could only ever contain VBScript and, for a variety

of reasons, they failed to find favor among developers.

Code declaration blocks are generally placed inside the head of your ASP.NET

page. The sample ASP.NET page shown in Figure 2.2, for instance, contains the

following code declaration block:

Visual Basic File: Hello.aspx (excerpt)

<script runat="server">

Sub Page_Load()

messageLabel.Text = "Hello World"

End Sub

</script>

Perhaps you can work out what the equivalent C# code would be:

C# File: Hello.aspx (excerpt)

<script runat="server">

void Page_Load()

{

messageLabel.Text = "Hello World";

}

</script>

The <script runat="server"> tag also accepts two other attributes. We can

set the language that’s used in this code declaration block via the language at-

tribute:

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Chapter 2: ASP.NET Basics