How to determine if a type is in the inheritance hierarchy

You can use the Type.IsAssignableFrom method.

In VB:

If GetType(Domain).IsAssignableFrom(GetType(DerivedThree)) Then

In C#:

if (typeof(Domain).IsAssignableFrom(typeof(DerivedThree)))

Why is nobody mentioning Type.IsSubclassOf(Type) ?

https://docs.microsoft.com/en-us/dotnet/api/system.type.issubclassof?view=netframework-4.7.2

Careful, it returns false if called for two equal types ;)

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