In C# grab URL parameters

How would I go about taking URL parameters from the server side?
I tried to use parameters from the Radzen but it failed to work like that, for example:
http://localhost:8000/return?test=RETURN-LV60&token=EC-7WU35&ReturnerID=YAGRVQM2

I haven't found a way to grab the parameters in C# yet... any tips?