Why do I (sometimes) have to reference assemblies referenced by the assembly I reference?

Question

I have an assembly A that defines an interface with some overloads:

public interface ITransform
{
    Point InverseTransform(Point point);
    Rect InverseTr         


        

Answer 1

The compiler needs to know what a System.Drawing.Point is in order to prove that it's not the correct overload (eg, if it has an implicit conversion).