mvc cant access repository classes from static functions in controller(mvc net c# Entity Frame work)

I working on .net MVC Entity Framework (Code First). I am not able to get Datacontext in repository classes functions when i call these functions from a static function in controller . I am getting the Exception
"An exception of type 'System.NullReferenceException' occurred in YYYYYY.Web.dll(Default project dll) but was not handled in user code
Additional information: Object reference not set to an instance of an object."
i need to call static functions since i had to call some functions asynchronously.Like Report generation
This works perfectly fine when called from a non static function in controller.
Thanks in advance Punnoose