ErrorMessage is ignored in DataAnnotations DataType Attribute

asp.net-mvc, data-annotations, error-handling

Solution

In MVC1 DataType attribute does not do what you'd expect, it looks like it does not in MVC2 either. Your best call is to have a string property representing the date, check it's validity there.

Here's a small excerpt from a project (using DataAnnotations and xVal):

private List<ErrorInfo> _errors;
        private List<ErrorInfo> Errors
        {
            get
            {
                if (_errors == null)
                    _errors = new List<ErrorInfo>();
                return _errors;
            }
            //set { _errors = value; }
        }

private string _startDateTimeString;

        /// <summary>
        /// A string reprsentation of the StartDateTime, used for validation purposes in the views.
        /// </summary>
        /// <remarks>
        /// If the user passes something like 45/45/80 it would be a valid mm/dd/yy format, but an invalid date,
        /// which would cause an InvalidOperationException to be thrown by UpdateModel(). By assigning dates to string properties
        /// we can check not only the format, but the actual validity of dates.
        /// </remarks>
        public string StartDateTimeString
        {
            get
            {
                return _startDateTimeString;
            }
            set
            {
                // Check whether the start date passed from the controller is a valid date.
                DateTime startDateTime;
                bool validStartDate = DateTime.TryParse(value, out startDateTime);
                if (validStartDate)
                {
                    StartDateTime = startDateTime;
                }
                else
                {
                    Errors.Add(new ErrorInfo("StartDateTime", "Provide a valid date for the start time."));
                }

                _startDateTimeString = value;
            }
        }

        partial void OnValidate(ChangeAction action)
        {
            if (action != ChangeAction.Delete)
            {
                Errors.AddRange(DataAnnotationsValidationRunner.GetErrors(this));

                if (StartDateTimeString != null)
                {
                    DateTime startDateTime;
                    if (!DateTime.TryParse(StartDateTimeString, out startDateTime))
                    {
                        Errors.Add(new ErrorInfo("StartDateTime", "Provide a valid date for the start time."));
                    }
                }

                if (Errors.Any())
                    throw new RulesException(Errors);
            }
        }
    }

It makes sense to have the check in both places in our project, but I just want to show you a concept.

Problem

I have a Model that is using DataAnnotations. Something like ``` public class Appointment { [Required(ErrorMessage="Please enter your name")] public string Name { get; set; } [Required(ErrorMessage="Please enter your appointment date?")] [DataType(DataType.Date, ErrorMessage="Appointment date is not a date")] public DateTime AppointmentDate { get; set; } } ``` The "Required" attributes respect the value in ErrorMessage; that is, if I don't enter a value, I am getting my "please enter" message. However, if I enter a string in the DateTime field, I am getting a standard system error message "The value 'blah' is not valid for AppointmentDate". I debugged through ASP.NET MVC code, and it seems that in the case of FormatException it doesn't pick the right display name from propertyMetadata. Either that, or I am missing something blatantly obvious :/ Did anybody run into this problem? Is it me, or is it just beta (I am using ASP.NET MVC 2 Beta)?

Original source