Possible Duplicate:
How to reference .NET 4.0 assembly within .NET 3.5 projects
Is there any way to ineteroperate a 4.0 assembly (a WPF interface) within a 3.5 application (an MFC Application). This application is giving us no end of trouble attempting to migrate it to 4.0.
They are running on different .NET runtimes and CLRs, so unfortunately no, this is not possible.