What are the major events in global.asax?

The Global.asax file in ASP.NET provides several major events that you can handle to perform custom actions at different stages of the application's lifecycle. Here are the major events in Global.asax along with examples:

1. Application_Start: This event occurs when the application is started for the first time or when the application pool is recycled. It is typically used for initializing application-wide resources or performing one-time setup tasks. For example:

   
   void Application_Start(object sender, EventArgs e)
   {
       // Initialize database connection
       Database.Initialize();
   
       // Register custom routes
       RouteConfig.RegisterRoutes(RouteTable.Routes);
   
       // Set application-wide settings
       GlobalConfiguration.Configure(WebApiConfig.Register);
   }
   

2. Application_End: This event occurs when the application is shutting down or the application pool is recycled. It is useful for performing cleanup tasks or releasing resources. For example:

   
   
   void Application_End(object sender, EventArgs e)
   {
       // Release application-wide resources
       Logger.Close();
       Database.Dispose();
   }
   
   

3. Session_Start: This event occurs when a new user session is started. It is useful for initializing session-specific data or performing any necessary setup tasks. For example:

   
   
   void Session_Start(object sender, EventArgs e)
   {
       // Initialize session variables
       Session["CartItemsCount"] = 0;
   }
   
   

4. Session_End: This event occurs when a user session is ending, either by timeout or explicitly. It is typically used for releasing session-specific resources or performing cleanup tasks. For example:

   
   
   void Session_End(object sender, EventArgs e)
   {
       // Release session-specific resources
       ShoppingCart.ClearItems(Session.SessionID);
   }
   
   

5. Application_Error: This event occurs when an unhandled exception is thrown within the application. It allows you to catch and handle the exception, log the error, and provide a user-friendly error page. For example:

   
   
   void Application_Error(object sender, EventArgs e)
   {
       Exception exception = Server.GetLastError();
       // Log the error
       Logger.Log(exception);
   
       // Redirect to custom error page
       Server.ClearError();
       Response.Redirect("~/Error.aspx");
   }
   

These are just a few examples of how you can handle major events in the Global.asax file. By writing custom logic within these event handlers, you can control various aspects of your ASP.NET application's behavior and perform necessary initialization, cleanup, error handling, and session management tasks.