Running .NET 3.5 built Mixed mode assemblies in .NET 4 using app config requires Framework 3.5 as well

Question

This is similar to already created thread here: Mixed mode assembly in .NET 4

Using the app config, I was able to force the assemblies to run on .NET 4. On an XP Mac

Answer 1

The reason is, that the way how it binds to mixed mode assemblies. Make sure you use the useLegacyV2RuntimeActivationPolicy="true" option in the startup-configuration of you app.config file (which I assume looks similar to the following):

See also: What does 'useLegacyV2RuntimeActivationPolicy' do in the .NET 4 config?