What is allowed in Visual Basic that's prohibited in C# (or vice versa)?

Question

This is code-related as in what the compiler will allow you to do in one language, but not allow you to do in another language (e.g. optional parameters in

Answer 1

In VB you can implement an interface with a method of any name - i.e. a method "Class.A" can implement interface method "Interface.B".

In C#, you would have to introduce an extra level of indirection to achieve this - an explicit interface implementation that calls "Class.A".

This is mainly noticeable when you want "Class.A" to be protected and/or virtual (explicit interface implementations are neither); if it was just "private" you'd probably just leave it as the explicit interface implementation.

C#:

interface IFoo {
    void B();
}
class Foo : IFoo { 
    void IFoo.B() {A();} // <====  extra method here
    protected virtual void A() {}
}

VB:

Interface IFoo
    Sub B()
End Interface
Class Foo
    Implements IFoo
    Protected Overridable Sub A() Implements IFoo.B
    End Sub
End Class

In the IL, VB does this mapping directly (which is fine; it is not necessary for an implementing method to share a name).