What is Global.asax?

The Global.asax file(also known as the ASP.NET application file) is an optional file that is located in the application's root directory and is the ASP.NET counterpart of the Global.asax of ASP.This file exposes the application and the session level events in ASP.NET and provides a gateways to all the application and the session level events in ASP.NET.This file can be used to implement the important application and session level events such as Application_Start,Application_End, Session_Start,Session_End,etc.