The global.asax file in ASP.NET

The global.asax file in ASP.NET as an application file, which is optional and allows us to write code that response to global application events raised by ASP.NET or by HttpModules. These events fire at various points during the lifetime of a web application, including when the application domain is first created.

The global.asax file resides in the root directory of an ASP.NET application. At run time, global.asax is parsed and compiled into a dynamically generated .NET Framework class derived from the HttpApplication base class.

The global.asax file looks very similar to a normal .aspx file. However, instead of containing HTML or ASP.NET tags, it contains event handlers that response to application events. Each ASP.NET application can have only one global.asax file. Once you place it in the appropriate website directory, ASP.NET recognizes it and uses it automatically.

The ASP.NET global.asax file can coexist with the ASP global.asa file.

Basic Application Events

S. No.	Event Handling Method	Description
1	Application_Start()	Application_Start() event occurs when the application starts, which is the first time it receives a request from any user. It doesn’t occur on subsequent requests. This event is commonly used to create or cache some initial information that will be reused later.
2	Application_End()	Application_End() event occurs when the application is shutting down, generally because the web server has restarted. You can insert cleanup code here.
3	Application_BeginRequest()	Application_BeginRequest() event occurs with each request the application receives, just before the page code is executed.
4	Application_EndRequest()	Application_EndRequest() event occurs with each request the application receives, just after the page code is executed.
5	Session_Start()	Session_Start() event occurs whenever a new user request is received and a session is started.
6	Session_End()	Session_End() event occurs when a session times out or is programmatically ended. This event is only raised if you are using in-process session state storage (the InProc mode, not the StateServer or SQLServer modes ).
7	Application_Error()	Application_Error() event occurs in response to an un-handled error.