It is more a razor/asp.net question than jsreport question.
I am not using razor so not sure.
I would guess you parse the json using json.net into a dynamic object and pass it as dynamic model to the view.
However, as I said, not an expert here.
However, it is just one way.
You can also start extra service - jsreport or jsreportonline and integrate from .net using jsreport.Client
This separation is more complex for the set up, but a bit cleaner on the other hand.
It is up to you what you will prefer.
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