One of the features that unfortunately did not
make it into the beta (but which we will add for the next update) is support so that you can expose custom error validation messages from your model classes (as
opposed to customizing them in the Controller like you can do today). We
are currently investigating a few ways to enable this - including adding support for the IDataErrorInfo interface, as well as support for the new Dynamic Data attributes
in the System.ComponentModel.DataAnnotations namespace.
One improvement that did make it into today's
beta, though, is that the default validation error messages are now more
end-user friendly (which hopefully eliminates the need to define custom
validation messages in a lot of cases):
Figure 20