Building the Http Module

In order to build an Http module we only need to implement
the IHttpModule interface. The following is a simple
LoggingHttpModule which log details when a web request start
and when web request end:

using System;
using System.Web;
using Microsoft.Practices.EnterpriseLibrary.Common.Configuration;
using Microsoft.Practices.EnterpriseLibrary.Logging;
 
namespace HttpModules
{
  public class LoggingHttpModule : IHttpModule
  {
    #region Members
 
    private LogWriter _writer;
 
    #endregion
 
    #region IHttpModule Members
 
    public void Dispose()
    {
      if (_writer != null)
      {
        _writer.Dispose();
      }
    }
 
    public void Init(HttpApplication context)
    {
      CreateLogWriter();
      context.BeginRequest += new EventHandler(context_BeginRequest);
      context.EndRequest += new EventHandler(context_EndRequest);
    }
 
    private void CreateLogWriter()
    {
      ConfigureEnterpriseLibraryContainer();
      _writer = EnterpriseLibraryContainer.Current.GetInstance<LogWriter>();
    }
 
    private void ConfigureEnterpriseLibraryContainer()
    {
      var builder = new ConfigurationSourceBuilder();
 
      builder.ConfigureInstrumentation().EnableLogging();
      builder.ConfigureLogging().WithOptions
             .LogToCategoryNamed("General")
               .WithOptions
               .SetAsDefaultCategory()
               .SendTo
               .FlatFile("Log File")
               .FormatWith(new FormatterBuilder()
               .TextFormatterNamed("Textformatter"))
                   .ToFile("file.log");
 
      var configSource = new DictionaryConfigurationSource();
      builder.UpdateConfigurationWithReplace(configSource);
      EnterpriseLibraryContainer.Current =
        EnterpriseLibraryContainer.CreateDefaultContainer(configSource);
    }
 
    void context_BeginRequest(object sender, EventArgs e)
    {
      _writer.Write(new LogEntry
      {
        Message = "BeginRequest"
      });
    }
 
    void context_EndRequest(object sender, EventArgs e)
    {
      _writer.Write(new LogEntry
      {
        Message = "EndRequest"
      });
    }
 
    #endregion
  }
}

Using The Module

In order to use the module all we need to do is to add a reference
to the class library that holds the LoggingHttpModule. Then we need
to register the module in the web.config file in the httpModules 
element like:

<httpModules>
    <add name="LoggingHttpModlue" type="HttpModules.LoggingHttpModule, HttpModules"/>
</httpModules>

That is it. Now the module will be executed whenever a request
start or end.