Error : Unable To Cast Object Of Type 'Object' To 'CTest'

I have

Public stack() As CTest

I want

Public stack() As Object

The latter is giving the error "Unable to cast object of type 'Object' to 'CTest'." when used:

Dim thestack As CTest() = testdatabase.getStack
Where testdatabase.getStack simply returns stack();
Public Function getStack() As Object()
Return stack
End Function

This fixes it, but it's not ideal (for me personally):

Dim thestack As Object() = testdatabase.getStack

So if I could keep the variable as-is (Public stack() As Object) and then do something along the lines of class.stack() = CTest I should be able to do Dim thestack As CTest() = testdatabase.getStack because the object array will programmatically have changed from Object to CTest.