Microsoft ASP.NET 4 : HttpModules (part 1) - Existing Modules & Implementing a Module

Writing a class implementing IHttpModule

Writing handlers for the events you want handled

Subscribing to the events

Configuring the module in web.config

To implement a timing module, open the Web application solution file for this article—UseApplication. To work, the module needs to exist in an assembly. It's easiest to write a completely separate assembly for the module. Add a project to the solution by clicking File, Add, New Project on the main menu. Make the project a Class Library and name the project TimingModule.

Visual Studio will add a class to the library named Class1. (The name of the file generated by Visual Studio is Class1.cs and the name of the class generated by Visual Studio is Class1.) Change the name of the file to Timer.cs and the name of the class to Timer. Place the code in the TimingModule namespace.

The module as generated by Visual Studio doesn't understand the ASP.NET types. Add a reference to System.Web to make the ASP.NET types available.

Add handlers for the beginning and ending of the request. You can borrow the code from Global.asax if you want. The signatures for the event's handlers are such that the methods have the return type of void and accept two arguments: an object and EventArgs.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web;

/// <summary>
/// Summary description for Timer
/// </summary>
namespace TimingModule {
   public class Timer
   {
      public Timer()
       {
       }
       public void OnBeginRequest(object o, EventArgs ea)
       {
               DateTime dateTimeBeginRequest = DateTime.Now;


         HttpContext ctx;
         ctx = HttpContext.Current;
         ctx.Items["dateTimeBeginRequest"] = dateTimeBeginRequest;
       }

       public void OnEndRequest(object o, EventArgs ea)
       {
         DateTime dateTimeEndRequest = DateTime.Now;

         HttpContext ctx;
         ctx = HttpContext.Current;
         DateTime dateTimeBeginRequest =
             (DateTime)ctx.Items["dateTimeBeginRequest"];

         TimeSpan duration = dateTimeEndRequest - dateTimeBeginRequest;

         ctx.Response.Write("<b>From the TimingModule: This request took " +
            duration.ToString() + "</b></br>");
       }
   }
}

					  

Add IHttpModule to the class's inheritance list. Add implementations for the methods Init and Dispose by right-clicking IHttpModule in the editor and clicking Implement Interface. The job performed by Init is to subscribe to events. The job performed by Dispose is to release any resources used by the module. (Dispose doesn't need to do anything in this example.)

public class Timer
         : IHttpModule
{
   public Timer()
   {
   }

   public void Init(HttpApplication httpApp)
   {
      httpApp.BeginRequest +=
         new EventHandler(this.OnBeginRequest);

      httpApp.EndRequest +=
         new EventHandler(this.OnEndRequest);
   }
   public void Dispose() { }

// ...
}

The Web site needs to know about the new module. Add a project-level reference (a reference to the new module) to the UseApplication Web application project so that you can use it from the page code. Right-click the UseApplication node in Solution Explorer and click Add Reference. In the Add Reference dialog box, click the Project tab and select TimingModule from the list, and then click OK. The following graphic shows the Add Reference dialog box:

Finally, mention the TimingModule in the web.config file. It needs to appear in the httpModules section, nested within the system.web section, like so:

<configuration>
 <system.web>
     <httpModules>
      <add name="TimingModule"
           type="TimingModule.Timer, TimingModule" />
          </httpModules>
</system.web>
</configuration>