If we use Asp.net Web Application (File -> New-> Project-> Asp.net Web Application) , we can add Global.asax as well as Global.asax.cs file.

However, if we use Asp.net Web site (File->New->Website->Asp.net Website), it is not the case. By default we will have Global.asax file only and not the Global.asax.cs file.

The structure of the Global.asax file is as under

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

<script runat="server">

    void Application_Start(object sender, EventArgs e) 
    {
        // Code that runs on application startup

    }
    
    void Application_End(object sender, EventArgs e) 
    {
        //  Code that runs on application shutdown

    }
        
    void Application_Error(object sender, EventArgs e) 
    { 
        // Code that runs when an unhandled error occurs

    }

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

    }

    void Session_End(object sender, EventArgs e) 
    {
        // Code that runs when a session ends. 
        // Note: The Session_End event is raised only when the sessionstate mode
        // is set to InProc in the Web.config file. If session mode is set to StateServer 
        // or SQLServer, the event is not raised.

    }       
</script>

So how can we add a Global.asax.cs file for a Asp.net Web site project? Let us observer the same in the below steps

Step 1:

Right click App_Code -> Add New Item -> Class -> Rename it as Global.cs . Then click on the Add button.

Step 2:

In the Global.cs file that got created, decorate it by inheriting the class from System.Web.HttpApplication

So the Global.asax.cs file will now look like

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

public class Global : System.Web.HttpApplication 
{
	public Global()
	{
		//
		// TODO: Add constructor logic here
		//
	}
}

We can add some events to it as under

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

/// 

/// Summary description for Global
/// 
public class Global : System.Web.HttpApplication 
{
	public Global()
	{
		//
		// TODO: Add constructor logic here
		//
	}

     protected void Application_Start(object sender, EventArgs e)
     {

     }

     protected void Session_Start(object sender, EventArgs e)
    {

    }

    protected void Session_End(object sender, EventArgs e)
    {

    }

    protected void Application_End(object sender, EventArgs e)
    {

    } 
}

Step 3:

Now, from the Global.asax file, remove the entire script code and change the

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

to

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

That’s it. Now run the application and it will work

Hope this helps atleast for the newbies. Happy coding.