c# 4.0 - Microsoft WF .NET ExpressionText causes validation errors -

this related workflow foundation .net 4.0. have found when setting expressiontext reserved keyword such "interface" or "class", underlying validation service in foundation throws validation message stating "one or more children have validation errors or warnings".

we setting expressiontext of argument this:

        argument inarg = argument.create(typeof(t), argumentdirection.in);          inarg.expression = new visualbasicvalue<t>         {             expressiontext = selecteditem,         };          mp.setvalue(inarg);  

any idea if known issue, , how can handle it?