Compiler Error C2811

'type1' : cannot inherit from 'type2', a ref class can only inherit from a ref class or interface class

You attempted to use an unmanaged class as a base class for a managed class.

The following sample generates C2811:

// C2811.cpp
// compile with: /clr /c
struct S{};
ref struct T {};
ref class C : public S {};   // C2811
ref class D : public T {};   // OK