What version of the control are you using? The CopyPaste sample calls the public bool PasteFromClipboard (
    float dx,
    float dy,
    bool unconnectedLinks
) method, which allow pasting unconnected links. I've added diagram.AllowUnconnectedLinks = true; to the constructor and copy/paste for such links works fine from what I can see.

Stoyan

This sample was created at a time when there weren't built-in clipboard methods (clipCopy was used for the Copy/Paste buttons too) , but we left it for the export selection code. Is exporting the selection what you need to use? Now you can implement this using the CopySelection and PasteSelection methods of Diagram to clone the selected items into a second Diagram, and then save that diagram into a file.

I hope that helps,
Stoyan