Error when using extension methods in C#

Question

I came across an issue that makes me think there is bug in the 3.0 framework. When I try to use extension methods I get the following error:

Missing compile         


        

Answer 1

I had a version of Elmah.Sandbox that was targetting .net 2.0 in an existing .Net 4.0 project. I added an extension method to my project and the build failed with the "Missing compiler required member" error message.

The Elmah.Sandbox dll was included as part of an early version of ElmahR. Once this was removed, it all built again.