How to force ValidationAttribute to mark specified object members as invalid?

Question

I've got my model which contains some members:

public class Address
{
   public Street { get; set;}
   public City { get; set; }
   public PostalCode { get; set; }
}

Now I've got my ValidationAttribute with IsValid method overrided like this:

protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
    var input = value as Address;

    if (string.IsNullOrEmpty(input.City))
        return new ValidationResult("City is required);

    if (!string.IsNullOrEmpty(input.PostalCode))
        if (string.IsNullOrEmpty(input.Street))
            return new ValidationResult("Stret is required");

    return ValidationResult.Success;
}

The problem is:

After validation my model state adds model error only to whole Adress member, but I need it to be added to specified members like city or street.

Any help with this will be appreciated... thanks!

Answer 1

you can add memberNames !

return new ValidationResult("City is required", new string[] { "City", "Street" });

EDIT : i've tested and found a solution : System.ComponentModel.IDataErrorInfo !! this doesn't work on the javascript client, but when submitting the result is what we attempted :) so keep using the ValidationResult with memberNames and :

public class myModel : System.ComponentModel.IDataErrorInfo
    {

        private Dictionary<string, List<ValidationResult>> errors;
        private bool IsValidated = false;

        private void Validate()
        {
            errors = new Dictionary<string, List<ValidationResult>>();
            List<ValidationResult> lst = new List<ValidationResult>();
            Validator.TryValidateObject(this, new ValidationContext(this, null, null), lst, true);
            lst.ForEach(vr =>
                {
                    foreach (var memberName in vr.MemberNames)
                        AddError(memberName, vr);
                });
            IsValidated = true;
        }
        private void AddError(string memberName, ValidationResult error)
        {
            if (!errors.ContainsKey(memberName))
                errors[memberName] = new List<ValidationResult>();
            errors[memberName].Add(error);
        }

        public string Error
        {
            get
            {
                if (!IsValidated)
                    Validate();

                return string.Join("\n", errors
                    .Where(kvp => kvp.Value.Any())
                    .Select(kvp => kvp.Key + " : " + string.Join(", ", kvp.Value.Select(err => err.ErrorMessage)))
                    );
            }
        }

        public string this[string columnName]
        {
            get
            {
                if (!IsValidated)
                    Validate();

                if (errors.ContainsKey(columnName))
                {
                    var value = errors[columnName];
                    return string.Join(", ", value.Select(err => err.ErrorMessage));
                }
                else
                    return null;
            }
        }

and now the current property is marked in error, and the memberNames too !

:D

Edit 2

In fact, you can keep simple DataAnnotations to inform client, and server side, you can add more complex business validation :

public class myModel : IValidatableObject
{
      public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
      {

            if (string.IsNullOrEmpty(input.City))
                  yield return new ValidationResult("City is required",new string[]{"prop1","prop2"});
            if (!string.IsNullOrEmpty(input.PostalCode))
                  if (string.IsNullOrEmpty(input.Street))
                        yield return new ValidationResult("Stret is required");
      }

note that the Validate method is called only when DataAnnotations are all valid !