HttpHandler :
Only one http handler executes and provides response
<--MapReuestHandler &
PostMapRequestHandler-->
Selection ------------------HttpHandlers---------------Execution
<-----determines events which are responsible for handling
httprequest------>
ASP .Net HttpHandler Selection and HttpHandler Executes
1. BeginRequest
2. ResolveRequestCache
3. MapRequestHandler
4. AcquireRequestState
5. RequestHandlerExecute
6. UpdateRequestCache
7. LogRequest
8. EndRequest
