You raise an interesting point about VB/C# compilation that I can't really speak to.  If you're looking for a solution, here's a way to do it from the question [How can I recognize a generic class?](https://stackoverflow.com/a/2478022/1366033)

Define these functions:



    Public Function IsSubclassOf(ByVal childType As Type, ByVal parentType As Type) As Boolean
        Dim isParentGeneric As Boolean = parentType.IsGenericType

        Return IsSubclassOf(childType, parentType, isParentGeneric)
    End Function

    Private Function IsSubclassOf(ByVal childType As Type, ByVal parentType As Type, ByVal isParentGeneric As Boolean) As Boolean
        If childType Is Nothing Then
            Return False
        End If

        If isParentGeneric AndAlso childType.IsGenericType Then
            childType = childType.GetGenericTypeDefinition()
        End If

        If childType Is parentType Then
            Return True
        End If

        Return IsSubclassOf(childType.BaseType, parentType, isParentGeneric)
    End Function

Call like this:

    Dim baseType As Type = GetType(MyBaseClass(Of ))
    Dim childType As Type = GetType(MyOtherChildClass)

    Console.WriteLine(IsSubclassOf(childType, baseType))
    'Writes: True

Here's a [Microsoft Connect Ticket](http://connect.microsoft.com/VisualStudio/feedback/details/95768/a-call-to-type-basetype-on-an-open-generic-hierarchy-will-produce-a-unexpected-typehandle) that might deal with this issue and give some explanation as to whether this was a feature or a bug of generic typing.

Although this case doesn't seem supported by the [`Type Of`](http://msdn.microsoft.com/en-us/library/0ec5kw18.aspx) documentation which states that for classes, typeof will return true if:

>*objectexpression* is of type *typename* or **inherits** from *typename*

When comparing types in VB the following works as expected and enables the current instance to be compared against a specific inherited class, in this case returning `False` (snippet from [LINQPad][1])

	Sub Main
		Dim a As New MyOtherChildClass
	
		a.IsType().Dump()
	End Sub
	
	' Define other methods and classes here
	MustInherit class MyBaseClass
		Public Function IsType() As Boolean
			Return TypeOf Me Is MyChildClass
		End Function
	End Class
	
	Class MyChildClass 
		Inherits MyBaseClass
	End Class
	
	Class MyOtherChildClass
		Inherits MyBaseClass
	End Class

However when generics are introduced the VB compiler fails with the error `Expression of type 'UserQuery.MyBaseClass(Of T)' can never be of type 'UserQuery.MyChildClass'.`

	' Define other methods and classes here
	MustInherit class MyBaseClass(Of T)
		Public Function IsType() As Boolean
			Return TypeOf Me Is MyChildClass
		End Function
	End Class
	
	Class MyChildClass 
		Inherits MyBaseClass(Of String)
	End Class
	
	Class MyOtherChildClass
		Inherits MyBaseClass(Of String)
	End Class

The equivalent code in **C#** compiles and allows the comparison, returning the correct result



	void Main()
	{
		var a = new MyOtherChildClass();
	
		a.IsType().Dump();
	}
	
	// Define other methods and classes here
	
	abstract class MyBaseClass<T>
	{
		public bool IsType()
		{
			return this is MyChildClass;
		}
	}
	
	class MyChildClass : MyBaseClass<string>
	{
	}
	
	class MyOtherChildClass : MyBaseClass<string>
	{
	}

Why does the VB compiler not allow this comparison?

  [1]: http://www.linqpad.net/