Can not connect to Sql database in C# asp mvc application with Entity Framework BUT the same code works with Winform application

First of all, please excuse me if it sounds too rooky. I consider myself novice in MVC applications.
I have ran into a strange problem and there does not seem to be any way out of this, at least so far..I have looked everywhere and left no stone unturned to get it worked. Finally I turned to this forum.
This is my first post, so any mistakes please overlook and guide me.

Determine whether running in ASP.NET or WinForms/console without System.Web

From a class library, I need to determine at run-time whether I’m running in an ASP.NET app or a WinForms/console app. There have been several other questions asked on the subject, but all of those solutions require adding a reference to System.Web. If at all possible, when running my console and WinForms apps, I don’t want to load the System.Web assembly into memory just for one line of code out of thousands.