DateAttribute

public class DateAttribute : DataTypeAttribute
{
    public DateAttribute()
        : base(DataType.Date)
    {
            
    }

    public string MonthProperty { get; set; }

    public string DateProperty { get; set; }

    public string EmptyErrorMessage { get; set; }

    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        var monthProperty = validationContext.ObjectType.GetProperty(MonthProperty);
        var dayProperty = validationContext.ObjectType.GetProperty(DateProperty);

        var year = (string)value;
        var month = (string)monthProperty.GetValue(validationContext.ObjectInstance);
        var date = (string)dayProperty.GetValue(validationContext.ObjectInstance);

        if (string.IsNullOrEmpty(year) || string.IsNullOrEmpty(month) || string.IsNullOrEmpty(date))
        {
            return new ValidationResult(EmptyErrorMessage);
        }

        DateTime result;

        if (!DateTime.TryParseExact(year + "/" + month + "/" + date, "yyyy/M/d", null, DateTimeStyles.None, out result))
        {
            return new ValidationResult(ErrorMessageString);
        }

        return null;
    }
}