Looking for Mocking tool ( open source) for .Net application

Question

I have to automate my already existing (production) application, which is implemented using Visual Studio 2010.

I am looking for some free (open source) Mocking tool which supports for Non Virtual members, b'coz my application does not have any virtual members and I can't change my application logic, I am trying with MOQ mocking tool, but it does not support non-virtual members.

Thanks in Advance!