AppDomain ad = AppDomain.CreateDomain("DLL Unload test");

ProxyObject obj = ProxyObject)ad.CreateInstanceFromAndUnwrap(@"UnloadDll.exe", "UnloadDll.ProxyObject");

obj.LoadAssembly();

obj.Invoke("TestDll.Class1", "Test", "It's a test");

AppDomain.Unload(ad);

obj = null;

class ProxyObject : MarshalByRefObject

{

    Assembly assembly = null;

    public void LoadAssembly()

    {

        assembly = Assembly.LoadFile(@"TestDLL.dll");

    }

    public bool Invoke(string fullClassName, string methodName, params Object[] args)

    {

        if(assembly == null)

            return false;

        Type tp = assembly.GetType(fullClassName);

        if (tp == null)

            return false;

        MethodInfo method = tp.GetMethod(methodName);

        if (method == null)

            return false;

        Object obj = Activator.CreateInstance(tp);

        method.Invoke(obj, args);

        return true;

    }

}