Is it possible to get all the test categories from mstest solution dll using reflection?

Is it possible to get all the test categories from mstest solution dll using reflection? I tried, Assembly testAssembly = Assembly.LoadFile(@"c:\Test.dll");

but when i attempt to get types from this assembly using, var types = testAssembly.GetTypes();

it throws ReflectionTypeLoadException. I believe once i get the types i can look for CutomAttribute 'TestCategoryAttribute'.