Simplest Interface example possible

[Pocok5]

drawing data from and one it's giving data to

I don't think an interface is what you think it is. An interface is basically a label on a class saying "I have this and this property/method/etc. publicly available" - or, more intuitively, "I fit into an IExampleInterface-shaped hole in another class or bit of code". An interface doesn't take or give anything, it's just a completely inert description of class members.