Validating datatypes... How/Where and custom error-string?

I don't quite understand how MVC 2 is validating the datatypes, or how I could inject my own error-string/language.

Given a date-field in a View-Model:

 public DateTime Appointment { get; set; }

I would get the following error if I fill in an invalid date into the form: The value '01开发者_如何转开发.03.20111' is not valid for Appointment.

I certainly know about DataAnnotations (DisplayName, Required etc.), but I don't know how the datatype-validation happens and where/how I could hook in?

Thx for any tipps sl3dg3

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That message comes from the ModelBinder. You can write your own custom model binders if you would like. Scott Hanselman has examples here and here.