When given a ..Generic.Dictionary, I know I can use (get thedict mykey). Is there a way to (set! thedict mykey myval) or assoc! or something other than .Contains and .Add. .Add throws an exception if key already there.

like (set! (.Item thedict) mykey myvalue) // could replace if I could figure out interop with the Item indexer // it is probably something very easy and I am making it harder