Does MonoDevelop has Class View Diagram?

Well, Visual Studio has a sort of view, that if you right click on a project, it will let you choose the option “Class Diagram View” which will let you see your project in UML.

What inherit what, who implement what interface and so on.

Does MonoDevelop has it too?

Have you looked at this http://forum.unity3d.com/threads/128355-Free-Plugin-for-Automatic-Documentation-of-your-project-through-Doxygen ?