I thought the problem was solved.
What exactly are you trying to do and what problem do you face?
I am trying to make a .gha that reads the karamba model, collect specific data and write it to a json. But somehow after trying all the suggestions, like different .net framework, place the gha in different folders, naming the gha after karamba wrt alphabetical order, it keeps saying “Invalid cast: Model >> Model”.
the problem that you report typically occurs when the karamba.gha or karamba.dll assembly are loaded twice. Normally this can be solved via the Rhino-command ‘GrasshopperDeveloperSettings’, unhooking ‘Memory load *.GHA…’ and restarting Rhino/Grasshopper.
The fact that the cast does not work shows that the assemblies are already loaded.
Unhooking the memory load doesn’t seem to make any difference. Also not when the .gha is placed in different locations.
It could be that the ‘karamba.gha’- or ‘karamba.dll’-files which are referenced by Grasshopper are not the same as those you reference via VisualStudio or the GH C#-component.
In order to try that out: uninstall Karamba3D and remove all ‘karamba.gha’ and ‘karamba.dll’ files from your harddisk that still might lie around there. Then reinstall Karamba3D and update the references.