How do I determine if System.Type is a custom type or a Framework type?

Question

I want to distinctly determine if the type that I have is of custom class type (MyClass) or one provided by the Framework (System.String).

Is there any way in refle

Answer 1

Not all framework classes start in the System namespace (they can also be Microsoft etc).

As such, you could probably compare the location of a known framework class with that of the type that you are testing such as:

  if (String.CompareOrdinal(
        Path.GetDirectoryName(typeof(String).Assembly.Location), 
        Path.GetDirectoryName(typeof(MyType).Assembly.Location)
      ) == 0)
  {
    //Framework Type
  }
  else
  {
    //3rd Party DLL
  }

Not the greatest solution; but safer than just testing if the namespace starts with System (I could create a namespace that starts with System that isn't a framework class).

Edit

Also, in addition to the above test, it wouldn't hurt to verify that the type is loaded from the Global Assembly Cache:

typeof(MyType).Assembly.GlobalAssemblyCache