What exactly does the .NET 4.0 runtime do if a .NET 4.0 executable contains a reference to a .NET 2.0 assembly?
Is the .NET 2.0 assembly run with the .NET 4.0 runtime (in other words, .NET 4.0 must be 100% API-compatible to .NET 2.0) or does the process somehow host the .NET 2.0 runtime and some magic happens to make the .NET 2.0 types transparently accessible to my .NET 4.0-based code?
They say it should work fine. Check out this.
来源：https://stackoverflow.com/questions/2653566/what-happens-when-net-4-0-references-a-net-2-0-assembly