gistfile1.cs

 SimSet setInst = (dynamic)new ObjectInstance("SimSet", "TestObject1")
 {
    Values =
    {
       Fish1 = "TestVal"
    }
 };

 SimObject inst = (dynamic)new ObjectInstance("SimObject", "TestObject2")
 {
    Values =
    {
       Fish1 = "TestVal2"
    }
 };
 setInst.add(inst);
 omni.Util._echo(setInst["Fish1"] + " " + inst["Fish1"] + " " + ((SimObject)setInst.getObject(0))["Fish1"]);
 // Outputs: TestVal TestVal2 TestVal2