I am trying to use IRIS Native API in .NET code I see following code snippet here https://docs.intersystems.com/irislatest/csp/docbook/DocBook.UI.Page.cl…

  IRISReference valueRef = new IRISReference(""); // set inital value to null string
  iris.ClassMethodString("%SomeClass","SomeMethod",valueRef);
  String myString = valueRef.value;               // get the method result

But IRISReference is not available as a type.

 What reference (dlls) do I need to add for that? I have InterSystems.Data.IRISClient.dll , what else do I need? what am I missing here?