in .NET when you pass a class instance/interface as a parameter do you pass one object or the full vtable

Question

If you are passing an interface or an instance of a class as a parameter, are we passing many objects or the full vtable, because once you call a method on the instance it need to recurse the vtable and call the appropriate one right?
How does this work?

Answer 1

You're ultimately passing a pointer to the object, which contains a pointer to the vtable. Well, basically.

Answer 2

This is an implementation detail, so I think you shouldn't rely on that !:)

btw, there's no such thing as "passing an interface in parameter". You always pass an object reference which can implement none, one or several interfaces.

Answer 3

You're passing a reference (by value). The exact representation of a reference is implementation-specific, but in most cases it will be a pointer :)

See http://yoda.arachsys.com/csharp/parameters.html for more details.

(I'm on a phone at the moment - if someone could reformat the link that would be helpful :)