Factor out repeated calls to context.Request and swallow "Request is not available in this context" HttpException that occurs in IIS Integrated Mode during Application_Start and End.

It is not possible to detect from the HttpContext object alone whether the Request is available except by catching the exception upon access or reading an internal property.
http://stackoverflow.com/questions/2609512/
Merge pull request #82 from whiteboxsoftware/whitebox/dev

Handle missing Request object during Application_Start