Using HttpModule instead of Global.asax

<%@ Application Language="C#" %>

<script runat="server">

    void Session_Start(object sender, EventArgs e)
    {


    }

</script>

public void Init(HttpApplication context)
{
    context.BeginRequest += new EventHandler(Begin_Request);
    IHttpModule sessionModule = context.Modules["Session"];
    if(sessionModule != null &&
        sessionModule.GetType() == typeof(System.Web.SessionState.SessionStateModule))
    {
        (sessionModule as System.Web.SessionState.SessionStateModule).Start
          += new EventHandler(CustomHttpModule_Start);
    }
}

<%@ Application Language="C#" CodeBehind="Global.asax.cs" Inherits="Global" %>

public class Global : System.Web.HttpApplication
{
  public Global()   {	}

  void Session_Start(object sender, EventArgs e)
  {
      // Code that runs when a new session is started
  }
}