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A code declaration block is a container for application logic used by an ASP.NET page.
It defines the member variables, event handlers, and custom functions that are to be used by the page.
Code declaration blocks are defined using <script> tags that contain the mandatory runat="server" declaration.
<script runat="server">
Code goes here...
</script>
The <script> tag accepts two optional attributes.
| language |
Specifies the language used in this code declaration block. This value can represent any .NET-compatible language, such as Visual Basic ( VB ), C#, or JScript.NET. |
| src |
Specifies the path and file name of a script file to load. When this attribute is used, any other code in the declaration block is ignored. |
<script runat="server" language="codelanguage" src="filepathname">
Code goes here...
</script>
The language attribute is used to specify the language of its contained code.
If no language is specified, this value defaults to the language configured for the base page or user control, set by using the @ Page and @ Control directives.
If no language is specified in the directive, ASP.NET defaults to VB.
<script runat="server" language="C#">
A <script> element can also be used to specify an external script file by using the src attribute.
When you define the src attribute, all content between the opening and closing tags of the <script> element is ignored. In this case, use a closing slash at the end of the opening tag.
<script runat="server" src="myScript.cs" />
With this method, the code declaration block is written in a separate file, usually referred to as the code-behind file.
This is particularly useful in cases where the external script file can be called by any page needing the code contained in the script.
The below demonstrates using a code declaration block to define event-handling logic for the enter button click event.
<html>
<script language="C#" runat="server">
void greetUser ( Object Src, EventArgs E ) {
message.Text = "Hi " + Name.Text + ", welcome to ASP.NET!";
}
</script>
<body>
<form runat="server">
Enter your name: <asp:textbox id="Name" runat=server />
<asp:button text = "Enter" onClick = "greetUser " runat="server" />
<p><asp:label id="message" runat=server />
</form>
</body>
</html>
<html>
<script language="VB" runat="server">
Sub greetUser ( Src As Object, e As EventArgs )
message.Text = "Hi " & Name.Text & ", welcome to ASP.NET!"
End Sub
</script>
<body>
<form runat="server">
Enter your name: <asp:textbox id="Name" runat=server />
<asp:button text = "Enter" onClick = "greetUser " runat="server" />
<p><asp:label id="message" runat=server />
</form>
</body>
</html> |
| |
C# |
VB |
The below shows using the src attribute to link a page to an external script file.
<script language="C#" runat="server" src="today.cs" />
<div align="center">
<p id="msg">Today is <%= now.ToString ( "f" ) %>.
<%= strGreeting %></p>
</div>
Code Render Blocks Authoring an ASP.NET Page