ASP.Net MVC 2 Model Validation Regex Validator fails - asp.net-mvc-2

Question

I have following property in my Model Metadata class:
[Required(ErrorMessage = "Spent On is required")]
[RegularExpression(#"[0-1][0-9]/[0-3][0-9]/20[12][0-9]",
ErrorMessage = "Please enter date in mm/dd/yyyy format")]
[DataType(DataType.Date)]
[DisplayName("Spent On")]
public DateTime SpentOn { get; set; }
But whenever I call ModelState.IsValid it always returns false because regex is not validating. I have matched the entered date (08/29/2010) against new regex using same pattern and it matches perfectly.
What am I doing wrong?

Answer 1

Actualy there is another workaround for this. You can simply subclass the RegularExpressionAttribute
public class DateFormatValidatorAttribute : RegularExpressionAttribute {
public DateFormatValidatorAttribute()
: base(#"[0-1][0-9]/[0-3][0-9]/20[12][0-9]")
{
ErrorMessage = "Please enter date in mm/dd/yyyy format";
}
public override bool IsValid(object value) {
return true;
}
}
in your Global.asax.cs on application start register the RegularExpression addapter for client side validation like so:
DataAnnotationsModelValidatorProvider.RegisterAdapter(
typeof(DateFormatValidatorAttribute),
typeof(RegularExpressionAttributeAdapter));
Now you get to have the build-in MVC regular exression validator client side and keep the DateTime as your property type

Answer 2

That's because regex applies to strings and not DateTime properties. If the user enters an invalid string which cannot be parsed to a DateTime instance from the model binder it will add a generic error message before your regex pattern executes.
You have a couple of possibilities:
Customize the error message in a resource file
Write a custom model binder
Use a string property (I feel guilty for proposing this :-))