Regex to substring then compare

Question

I have the below code in my mvc application:

[Required(ErrorMessageResourceName = "NumberRequired",  ErrorMessageResourceType = typeof (Messages))]
[RegularExpression("^[0-9]{16}$", ErrorMessageResourceName = "NumberRequired", ErrorMessageResourceType = typeof (Messages))]
public string number{ get; set; }

[Required(ErrorMessageResourceName = "LastFourRequired", ErrorMessageResourceType = typeof(Messages))]
[RegularExpression("^[0-9]{4}$", ErrorMessageResourceName = "LastFourRequired", ErrorMessageResourceType = typeof(Messages))]
public string lastfour{ get; set; }

My problem is i need to validate the lastfour. It must be equal to the last four digit of number. I need to do that validation in this block of code.

Can somebody help me? Thanks in advance!

Answer 1

First thing is, if LastFour is extract same as the last four digits of PAN , why do you need LastFour property. you can just substring that part and get the last four digits.

But if you really need to do it, You can create a custom attribute for this,

public class LastFourDigitsAttribute : ValidationAttribute, IClientValidatable
{
    private string panPropertyname;

    public LastFourDigitsAttribute(string pan)
        : base()
    {
        if (string.IsNullOrEmpty(pan))
        {
            throw new ArgumentNullException("pan");
        }

        this.panPropertyname = pan;
    }

    public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
    {
        yield return new ModelClientValidationRule
        {
            ErrorMessage = ErrorMessage,
            // This is the name of the method added to the jQuery validator method (must be lower case)
            ValidationType = "lastfour"
        };
    }

    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        if (value != null)
        {
            PropertyInfo panPropertyInfo = validationContext.ObjectInstance.GetType().GetProperty(panPropertyname);

            if (panPropertyInfo != null)
            {
                var panPropertyValue = panPropertyInfo.GetValue(validationContext.ObjectInstance, null);

                if (panPropertyValue != null)
                {
                    if (value.ToString() != panPropertyValue.ToString().Substring(panPropertyValue.ToString().Length - 4);)
                    {
                        return new ValidationResult(ErrorMessage);
                    }
                }
            }
        }

        return ValidationResult.Success;
    }
}

Usage,

[LastFourDigits("PAN", ErrorMessageResourceName = "CustomerEnrollment_CardLastFourInvalidMessage", ErrorMessageResourceType = typeof(Messages))]
[Required(ErrorMessageResourceName = "CustomerEnrollment_CardLastFourRequiredMessage", ErrorMessageResourceType = typeof(Messages))]
[RegularExpression("^[0-9]{4}$", ErrorMessageResourceName = "CustomerEnrollment_InvalidLastFour", ErrorMessageResourceType = typeof(Messages))]
public string LastFour { get; set; }