Global.asax is a special file in ASP.NET applications that acts as the application's global file. It contains code that executes at various stages of the application's lifecycle, allowing you to handle events like:
* Application Start: Code in `Application_Start` runs when the application starts, allowing you to initialize things like databases, caching, and configuration.
* Application End: Code in `Application_End` runs when the application shuts down, allowing you to perform cleanup tasks.
* Session Start: Code in `Session_Start` runs when a user's session starts, allowing you to set session variables or perform other initialization for the user's session.
* Session End: Code in `Session_End` runs when a user's session ends, allowing you to perform cleanup tasks related to the session.
* Error Handling: You can handle application-level errors in `Application_Error`.
While it's a common practice to use Global.asax, it's not essential for ASP.NET applications. However, it's often used for handling events and customizing application behavior.