Inject application-specific code into ASP.NET module

We often write ASP.NET modules to customize ASP.NET processing pipeline - extend security, etc.

   1: public class ExampleModule : IHttpModule

   2:  {

   3:      #region IHttpModule Members

   4:  

   5:      public void Dispose() { }

   6:  

   7:      public void Init( HttpApplication context )

   8:      {

   9:          context.BeginRequest += new EventHandler( context_BeginRequest );

  10:      }

  11:  

  12:      void context_BeginRequest( object sender, EventArgs e )

  13:      {

  14:          // extend the processing pipeline by providing

  15:          // custom code for particular events, in this case

  16:          // the BeginRequest event

  17:      }

  18: }

However, as modules are static, in a sense that a module is active or inactive in processing pipeline, applications which "host" modules are dynamic, in a sense that different applications work under different conditions.

The issue we've faced recently was to inject a custom, application specific code into module:

   1: void context_BeginRequest( object sender, EventArgs e )

   2: {

   3:     // how to call an application-defined code

   4:     // but do it so that the module is not

   5:     // rewritten everytime application changes

   6:     

   7:     // ?

   8: }

The solution we've came up with was rather simple: we've used a custom provider to provide application-specific code.

   1: <system.web>

   2:     <specificProvider defaultProvider="ApplicationSpecificProvider">

   3:         <providers>

   4:             <add name="ApplicationSpecificProvider" type="Namespace.ApplicationSpecificProvider" />

   5:         </providers>

   6:     </specificProvider>

This way we can configure different providers on the application level but still be able to write generic module code:

   1: void context_BeginRequest( object sender, EventArgs e )

   2: {

   3:     HttpApplication app = (HttpApplication)sender;

   4:  

   5:     SpecificProvider.DoSpecificOperation( app );

   6: }