Hi,
One of the major changes in IIS 7.0 is that the HTTP context is not available in the application_start event. If you try to work with the http context (with the help of Httpcontext.current) in the application_start event in global.asax then you will receive an ASP.NET 500 – Server Error: Request is not available in this context.
In IIS 7.0 the Application Initialization has been decoupled from the request that has triggered the application start and hence the request is not available in the vent. In the classic mode , it was possible for us to indirectly access the request as the Asp.net initialization directly coupled with the request for which the application was started.