just one Problem: in Visual Basic I got this Error:
The type 'GH_IO.GH_ISerializable' is defined in an assembly that is not referenced. You must add a reference to assembly 'GH_IO, Version=1.0.0.0, Culture=neutral,
I referenced my Grasshopper.dll(version 1.0.0.20). Where I get this older version of the dll? Is it really necessary?
I don't think you need an older version of the dll, but a completely separate one. Add a reference and choose GH_IO.dll, which should be in the same location as the Grasshopper.dll