Textbox maintains ModelState value and does not get replaced with parameter.
If I were to utilise the following
the ViewData would get ignored on Post. Use of reflector and regenerating extension methods show that the ViewData would get ignored and the value would be onbtained from ModelState.
Unfortunately to get it working I had to do the following
ModelState.SetModelValue("Message", new ValueProviderResult(Message, Message, System.Globalization.CultureInfo.CurrentCulture));
which is potentially buggy and messes up state.