The CodeBehind Attribute

If you find and view the .asmx page that VS.NET automatically generates and places on your server, you'll notice that the WebService directive includes an additional attribute called CodeBehind. (Unfortunately, you cannot view this .asmx page from Visual Studio .NET; instead, you'll need to look at the file placed on your web server in the c:\inetpub\wwwroot\HelloWorldService folder). In our example, it looks like this (except it's all on a single line):

<%@ WebService Language="c#"




    Codebehind="HelloWorldService.asmx.cs"




    Class="ProgWS.Ch02.HelloWorldService" %>

This unfortunate choice for an attribute name often confuses developers new to ASP.NET, who often assume that it is used in some way by ASP.NET to locate the code-behind file (indeed, the Microsoft Visual Studio documentation would lead you to believe this to be the case). In fact, this is not the case. This attribute is a Visual Studio .NET-specific attribute and is used by VS.NET to match the .asmx page to the associated source code file. This attribute has nothing to do with ASP.NET. In fact, ASP.NET completely ignores this attribute when processing a page request.