Caught: System.InvalidOperationException: The argument of type ‘XXX‘ cannot be used. Make sure that it is declared on an activity.
at System.Activities.Argument.ThrowIfNotInTree()
at System.Activities.OutArgument`1.Set(ActivityContext context, T value)

Reasoon: Check the parameters here... must be something mismatched or wrong. 

metadata.AddArgument(new RuntimeArgument("AAAA", typeof(BBB), CCC.Out));