Mixed Mode Assembly Issue with Class Library

Question

I have a class library project, I have to reference an assembly in my class library project which targets v2.0.50727, then ultimately calling my class library from a project which is using .Net 4 version.

When the application runs, it gives error “Mixed mode assembly is built against version 'v2.0.50727' of the runtime and cannot be loaded in the 4.0 runtime without additional configuration information.”

I know i can add attributes in app.config to avoid this error, but in my case, this is class library which has no app.config.

I tried changing my class library to .net framework 2, but it is still showing error.

When I change target framework of main application from .net 4 to .net 3.5, compiler gives error on following line:

using System.ComponentModel.Composition;

What should I do ?

Answer 1

I ended up with changing my DLL to form-less winform EXE file which can accept command line arguments to replicate class library constructor arguments functionality. I supplied following attributes in my exe app.config file to avoid mixed mode assembly error:

<startup useLegacyV2RuntimeActivationPolicy="true">
  <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
</startup>