ASP.NET MVC [RegularExpression] Attribute Not Functioning on Entire String Match

Question

I can't seem to find a similar topic on Stack Overflow regarding this, so here goes:

Why is it when I specify against my ASP.NET MVC view model class the following definition:

[Required]
[RegularExpression(@"\A\d{3,4}\Z",
   ErrorMessage = "The security code (CVN) must be between 3 - 4 digits long.")]
[Display(Name = "Card Security Code (CVN)")]
public string CardCVN { get; set; }

That on my unobtrusive client side validation test the regular expression cannot be validated? (and subsequently displays a form field error).

It seems as soon as my regex is changed to [RegularExpression(@"\d{3,4}"... removing the entire string matching technique, it matches perfectly? and it seems the jquery validation that renders, even though it doesn't apply \A or \Z it matches only on entire string match anyway (doing what I originally needed!); Am I missing something?

Thanks.

Answer 1

On the client side, the regex is executed by JavaScript, and JS doesn't support \A, \Z or \z. You could use ^ and $ instead, but you shouldn't need to. Regexes used in validators are usually anchored at both ends automatically. I'm pretty sure that's the case with ASP.NET MVC.