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

This problem is indeed caused by an incorrect reference to version 2 of System.Core . This is normally caused when upgrading from an earlier version of .NET to .NET 3.5 . If it is a website that you are experiencing this problem in then it can be remedied by following the steps below:

1) In web.config add a reference to System.Core v3.5:

2) In web.config add the following as a child of configuration: