Application & Session Events in the Global.asax File
Programmers familiar with ASP will know about the global.asa file. It's the place where application level events are handeled. The global.asax file is the ASP.Net equivalent and it can be found in the root directory of an ASP.Net application.
Here is the list of events you can call. By calling them you are actually overriding the event that is exposed by the HttpApplication base class.
Application_Start: As with traditional ASP, used to set up an application environment and only called when the application first starts.
Application_Init:This method occurs after _start and is used for initializing code.
Application_Disposed: This method is invoked before destroying an instance of an application.
Application_Error: This event is used to handle all unhandled exceptions in the application.
Application_End: Again, like classic ASP, used to clean up variables and memory when an application ends.
Application_BeginRequest: This event is used when a client makes a request to any page in the application. It can be useful for redirecting or validating a page request.
Application_EndRequest: After a request for a page has been made, this is the last event that is called.
Application_PreRequestHandlerExecute: This event occurs just before ASP.Net begins executing a handler such as a page or a web service. At this point, the session state is available.
Application_PostRequestHandlerExecute: This event occurs when the ASP.Net handler finishes execution.
Application_PreSendRequestHeaders: This event occurs just before ASP.Net sends HTTP Headers to the client. This can be useful if you want to modify a header
Application_PreSendRequestContent: This event occurs just before ASP.Net sends content to the client.
Application_AcquireRequestState: This event occurs when ASP.Net acquires the current state (eg. Session state) associated with the current request.
Application_ReleaseRequestState: This event occurs after ASP.NET finishes executing all request handlers and
causes state modules to save the current state data.
Application_AuthenticateRequest: This event occurs when the identity of the current user has been established as valid by the security module .
Application_AuthorizeRequest: This event occurs when the user has been authorized to access the resources of the security module .
Session_Start: As with classic ASP, this event is triggered when any new user accesses the web site.
Session_End: As with classic ASP, this event is triggered when a user's session times out or ends. Note this
can be 20 mins (the default session timeout value) after the user actually leaves the site.