Hi RodWing,
the assemblies you have to always reference (import) in your NET add-in project are:
\MicroStation\assemblies\ECFramework\Bentley.General.1.0.dll
\MicroStation\assemblies\bentley.interop.microstationdgn.dll
\MicroStation\assemblies\bentley.microstation.dll
\MicroStation\assemblies\bentley.microstation.interfaces.1.0.dll
\MicroStation\ustation.dll
I don't know where Bentley.MicroStation.WinForms comes, I don't see such assembly on my hard drive. Adapter class, required for WinForm usage in MicroStation, is in bentley.microstation.dll.
[Edited] If you want to add docking feature to your dialogs, you have to reference also \MicroStation\assemblies\ECFramework\bentley.windowing.dll, where WindowsManager class is stored. If you plan to use dialogs without docking and standard Tool Settings dialog, this assembly is not required.
With regards,
Jan