Hi Stephen, it isn't currently in the near or mid-term roadmap for Pro to have a charting API in the Pro .Net SDK. This could perhaps be in our long term plan if there is enough user demand. I would encourage you to add your thoughts to an ArcGIS Idea, which will allow others to see and comment and add fuel to the fire
I would like to add that programmatic charting in ArcGIS Pro has already started, but through the Python/ArcPy library. Chart—ArcPy Classes | ArcGIS Desktop We started with ArcPy because the first request we heard was to make charts via geoprocessing script tools built with Python.
Just out of curiosity can you explain your business case for creating charts using the .Net SDK? What kind of charts are you making, what interaction pattern do you want, etc. If we understand your use case it will help us design and understand why this work should be a priority. This would also be great info to add to the ArcGIS Idea if you can create one.
Thanks,
Pro Charts dev team