If we use interpreter.SetDefaultNumberType(DefaultNumberType.Decimal); as in code below.

interpreter = new Interpreter().SetDefaultNumberType(DefaultNumberType.Decimal);

After this if we try to evaluate below string for a loaded variable strVariable , Below expression will not evaluate.

strVariable.Substring(0, 40)

if we create the interpreter with this interpreter = new Interpreter() then above expression will evaluate.

I have tried to add reference for the string and Math lib as below , but it still does not work , it only works if we remove the SetDefaultNumberType option.

 interpreter = interpreter.Reference(typeof(System.String));
 interpreter = interpreter.Reference(typeof(System.Math));

can someone help on this issue. as we need to set Default Number Type and also have some access to libraries for extension methods etc.