Question

I have to validate a string that’s supposed to contain an hour number (e.g. 00 to 23).

I hence set an annotation like:

 [RegularExpression("[01]?[0-9]|2[0-3]", ErrorMessage = "Error")]
 public string JobStartHour {...}

Unfortunately, this regex doesn’t match the inputs from 20 to 23, as it’s supposed to do (IMHO).

Doesn’t this RegularExpression attribute use the plain old Regex.IsMatch ?

Regex.IsMatch("22", "[01]?[0-9]|2[0-3]")

returns true…

Edit: I know, using a string isn’t the best idea so as to store a number, nevertheless, this regex issue is annoying.

Answer 1

Don’t know why this regex isn’t correctly interpreted, but a solution is to implement a CustomValidation, which is pretty handy.

   [CustomValidation(typeof(MyCustomValidation), "Validate24Hour")]
     public string JobStartHour {...}

...

  public class MyCustomValidation
    {
        public static ValidationResult Validate24Hour(string candidate)
        {
            bool isValid = false;
         ...
            if (isValid)
            {
                return ValidationResult.Success;
            }
            else
            {
                return new ValidationResult("Error");
            }
        }
   }