Hi Viv,

> I don't see why not - AFAICS no strong-typing rules are being broken.

But they are...

Test x = new Test();
ITest y = (ITest) x;
x.Parent.MethodOfDerivedClass();
y.Parent.MethodOfDerivedClass();

The first method call of MethodOfDerivedClass() would need to work since x.Parent is defined as being of type DerivedClass. The second method call would fail, though, because the interface returns the base class. In both cases, however, the code calls exactly the same Parent getter because the interface is implemented implicitly. So, you have the same method but two signatures. If that doesn't violate strong typing, I don't know what else would... The compiler can't do an implicit cast here.