Compare Dates DataAnnotations Validation asp.net mvc

Question

Lets say I have a StartDate and an EndDate and I wnt to check if the EndDate is not more then 3 months apart from the Start Date

public class DateCompare : V         


        

Answer 1

The Attribute

public class CompareValidatorAttribute : ValidationAttribute, IInstanceValidationAttribute
{
    public CompareValidatorAttribute(string prefix, string propertyName) {
        Check.CheckNullArgument("propertyName", propertyName);

        this.propertyName = propertyName;
        this.prefix = prefix;
    }

    string propertyName, prefix;

    public string PropertyName
    {
        get { return propertyName; }
    }

    public string Prefix
    {
        get { return prefix; }
    }

    #region IInstanceValidationAttribute Members

    public bool IsValid(object instance, object value)
    {
        var property = instance.GetType().GetProperty(propertyName);

        var targetValue = property.GetValue(instance, null);
        if ((targetValue == null && value == null) || (targetValue != null && targetValue.Equals(value)))
            return true;

        return false;
    }

    #endregion

    public override bool IsValid(object value)
    {
        throw new NotImplementedException();
    }
}

The Interface

public interface IInstanceValidationAttribute
{
    bool IsValid(object instance, object value);
}

The Validator

public class CompareValidator : DataAnnotationsModelValidator
{
    public CompareValidator(ModelMetadata metadata, ControllerContext context, CompareValidatorAttribute attribute)
        : base(metadata, context, attribute)
    {
    }

    public override IEnumerable Validate(object container)
    {
        if (!(Attribute as IInstanceValidationAttribute).IsValid(container, Metadata.Model))
            yield return (new ModelValidationResult
            {
                MemberName = Metadata.PropertyName,
                Message = Attribute.ErrorMessage
            });
    }

    public override IEnumerable GetClientValidationRules()
    {
        var rule = new ModelClientValidationRule() { ErrorMessage = Attribute.ErrorMessage, ValidationType = "equalTo" };
        rule.ValidationParameters.Add("equalTo", "#" + (!string.IsNullOrEmpty(Attribute.Prefix) ? Attribute.Prefix + "_" : string.Empty)+ Attribute.PropertyName);

        return new[] { rule };
    }
}

Register it:

DataAnnotationsModelValidatorProvider.RegisterAdapter(typeof(CompareValidatorAttribute), typeof(CompareValidator));