Dynamically apply validation rules at runtime with ASP.NET MVC 4

Question

I\'ve been working in WebForms for years but I\'m fairly new to .NET\'s flavor of MVC. I am trying to figure out how to apply dynamic validation rules to members of my model

Answer 1

As i said in my comment above i have done something similar using reflection. You can ignore some of it, you probably don't need the dictionary for example, as that was just a way of giving them custom translatable messages.

Server side code:

 private static Dictionary _requiredValidationDictionary;

 private static Dictionary RequiredValidationDictionary(UserBase model)
 {
      if (_requiredValidationDictionary != null)
          return _requiredValidationDictionary;

      _requiredValidationDictionary = new Dictionary
      {
             { model.GetPropertyName(m => m.Publication), ErrorMessageToken.PublicationRequired},
             { model.GetPropertyName(m => m.Company), ErrorMessageToken.CompanyRequired},
             { model.GetPropertyName(m => m.JobTitle), ErrorMessageToken.JobTitleRequired},
             { model.GetPropertyName(m => m.KnownAs), ErrorMessageToken.KnownAsRequired},
             { model.GetPropertyName(m => m.TelephoneNumber), ErrorMessageToken.TelephoneNoRequired},
             { model.GetPropertyName(m => m.Address), ErrorMessageToken.AddressRequired},
             { model.GetPropertyName(m => m.PostCode), ErrorMessageToken.PostCodeRequired},
             { model.GetPropertyName(m => m.Country), ErrorMessageToken.CountryRequired}
      };
      return _requiredValidationDictionary;

  }

  internal static void SetCustomRequiredFields(List requiredFields, UserBase model, ITranslationEngine translationEngine)
  {
      if (requiredFields == null || requiredFields.Count <= 0) return;
      var tokenDictionary = RequiredValidationDictionary(model);
      //Loop through requiredFields and add Display text dependant on which field it is.
  foreach (var requiredField in requiredFields.Select(x => x.Trim()))
  {
      ILocalisationToken token;

      if (!tokenDictionary.TryGetValue(requiredField, out token))
         token = LocalisationToken.GetFromString(string.Format("{0} required", requiredField));

      //add to the model.
      model.RequiredFields.Add(new RequiredField
      {
         FieldName = requiredField,
         ValidationMessage = translationEngine.ByToken(token)
      });
      }
  }

  internal static void CheckForRequiredField(ModelStateDictionary modelState, T fieldValue, string fieldName,                                                            IList requiredFields,                                                          Dictionary tokenDictionary)
   {
        ILocalisationToken token;
        if (!tokenDictionary.TryGetValue(fieldName, out token))
           token = LocalisationToken.GetFromString(string.Format("{0} required", fieldName));
        if (requiredFields.Contains(fieldName) && (Equals(fieldValue, default(T)) || string.IsNullOrEmpty(fieldValue.ToString())))
             modelState.AddModelError(fieldName, token.Translate());
   }

  internal static void CheckForModelErrorForCustomRequiredFields(UserBase model,                                                                             Paladin3DataAccessLayer client, ICache cache,                                                                             ModelStateDictionary modelState)
  {

      var requiredFields = Common.CommaSeparatedStringToList                          (client.GetSettingValue(Constants.SettingNames.RequiredRegistrationFields, cache: cache, defaultValue: String.Empty, region: null)).Select(x => x.Trim()).ToList();
      var tokenDictionary = RequiredValidationDictionary(model);

      foreach (var property in typeof(UserBase)             .GetProperties(BindingFlags.Instance |                                               BindingFlags.NonPublic |                                               BindingFlags.Public))
      {
            CheckForRequiredField(modelState, property.GetValue(model, null), property.Name, requiredFields, tokenDictionary);
      }
  }

On the model we have a List which is basically a class with two strings, one for the field name and one for the error message.

Once you have passed the model into the view you need a bit of jQuery to add the validation stuff to the page if you want to do the check server side.

Client side code:

   $("#YOURFORM").validate();
        for (var x = 0; x < requiredFields.length; x++) {
            var $field = $('#' + requiredFields[x].FieldName.trim());

            if ($field.length > 0) {
                $field.rules("add", {
                      required: true,
                      messages: {
                           required: "" + requiredFields[x].ValidationMessage  
                           //required: "Required Input"
                      }
                });

            $field.parent().addClass("formRequired"); //Add a class so that the user knows its a required field before they submit

                 }

          }

Apologies if any of this is not very clear. Feel free to ask any questions and I will do my best to explain.