Returning or inheriting a generic that contains a nested class

Question

I am noticing some extremely strange behaviour when using a class layout that looks like this:

// Contents of assembly A:
public class MyParentClass
{
    public class NestedClass
    {
    }
}

// Contents of assembly B:
public class AnotherClass : List<MyParentClass.NestedClass>
{
}

I can add assembly A as a dependency of assembly B. This example will compile without any error messages, but when it comes to, for example, loading assembly B as a reference for unit testing, I will receive this error when it comes time to compile unit tests:

Could not load file or assembly 'AssemblyB, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified.

The assembly that this code generates does actually work, and I can run through the generated DLL with Redgate Reflector and see my code as expected, but the unit tests refuse to load it.

I am almost positive that this issue is to do with the fact that I am calling a nested class that is in another assembly, and I will probably end up refactoring this design anyway, but I would really like to know why this does not work as expected. If there was a problem with using the classes in this fashion, I would expect the compiler to throw an exception.

Thank you for your time.

Answer 1

Is "Copy Local" enabled for that reference? I assume that your test project testing assembly B doesn't have a copy of assembly A. Setting "Copy Local" to true on the references should copy the assemblies, so that they can be found correctly when compiling (and finally running) the tests.

Answer 2

I doubt that this is anything to do with nested classes - just a lack of transitive dependencies being surfaced in .NET.

Basically, if you're going to use AnotherClass in one project, you'll need to explicitly add a reference to both AssemblyB and AssemblyA . That way both should be copied and loaded appropriately.

If that doesn't help, you could try enabling fusion logging .

Answer 3

You get this error message in visual studio 2010 if your project has target framework set to "Framework 4 Client Profile" and the linked dll has a target Framework "Framework 4".

Check that in your project settings.