Hi, My Visual C++ 2010 project uses an assembly (dll) which is compiled against v2.0.50729 of CLR. When I target the project for DotNet Framework 4.0, I get the following error message: Mixed mode assembly built against version v2.0.50727 of the runtime cannot be loaded in the 4.0 runtime without addition configuration information. I understand that the runtime policy for DotNet Framework is causing this error. I added app.config file to the VC++ project and edited the startup tag like this: but this doen't solve the problem. I guess that the VC++ project is not picking up the app.config file. Is there anything wrong that I am doing? Any known issues with VC 2010. The same thing works fine for VC# 2010.