Template tree in C# which is using patterns like visitors

at the moment, we designing a new component for our framwork which is written in C#. What we need is a tree to manage big structures (e.g. CAD structures). We would like use a tree which implements the composite and visitor patterns. Do everone know about a template or a framework which we coud use or have we implement our own base classes?

Further requirements for the tree: - do a cycle check - allow to reference one node in more locations (in CAD, one part is refrenced by many assemblies).

Thanks for your suggestions.