Show model property name in custom validation [Answered] RSS

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  vkagrawal

  Member

  7 Points

  75 Posts

  Show model property name in custom validation

  Feb 28, 2021 03:28 PM|vkagrawal|LINK

  Hi,

  I have a model with few properties and I am adding custom validation on some of its properties. Everything is fine, it is validating as expected.

  Only problem I see is in custom validators I am not able to get the model properties name as we can get that with in built validators.

  Below is code sample

  [Display(Name = "Status")]
  [RequiredIfNot(1, ErrorMessage = "Status is required")]
  public short? Status { get; set; }

  public class RequiredIfNotAttribute : ValidationAttribute, IClientModelValidator
  {
    // other code removed to keep it short
  
   protected override ValidationResult IsValid(object value, ValidationContext validationContext)
          {
              ErrorMessage = ErrorMessageString;
              short currentValue = Convert.ToInt16(value);
        
              // validation logic
             bool validationPassed = false;
              if (!validationPassed)
                  return new ValidationResult(ErrorMessage);
             else
                  return ValidationResult.Success;
          }
   }

  if I use [RequiredIfNot(1, ErrorMessage = "{0} is required")] then it shows error message as it is '{0} is required' rather than 'Status is required'

  I could pass in properties's name using nameof(Status) and replace {0} with that in validator but I want to align with built in validators.

  Thanks 

• • Reply
  YihuiSun

  Contributor

  3040 Points

  863 Posts

  Re: Show model property name in custom validation

  Mar 01, 2021 02:49 AM|YihuiSun|LINK

  Hi vkagrawal, 

  You need to use the ModelMetadata.Name property and the ValidationContext.MemberName property to get the name of the property. Then, you need to use String.Format to convert the value of the object into a string according to the specified format, and then insert it into another string.

  The following is an example, you can refer to it.

  RequiredIfNotAttribute

      public class RequiredIfNotAttribute : ValidationAttribute, IClientModelValidator
      {
          public int v;
  
          public RequiredIfNotAttribute(int v)
          {
              this.v = v;
          }
  
          public void AddValidation(ClientModelValidationContext context)
          {
              if (context == null)
              {
                  throw new ArgumentNullException(nameof(context));
              }
              context.Attributes.Add("data-val", "true");
              context.Attributes.Add("data-val-required", String.Format(ErrorMessageString,context.ModelMetadata.Name));
          }
  
          protected override ValidationResult IsValid(object value, ValidationContext validationContext)
          {
              ErrorMessage = String.Format(ErrorMessageString,validationContext.MemberName);
              short currentValue = Convert.ToInt16(value);
  
              // validation logic
              bool validationPassed = false;
              if (!validationPassed)
                  return new ValidationResult(ErrorMessage);
              else
                  return ValidationResult.Success;
          }
      }

  Model

      public class TestCustomModel
      {
          [Display(Name = "StatusTest")]
          [RequiredIfNot(1, ErrorMessage = "{0} is required")]
          public short? Status { get; set; }
      }

  Controller

      public class CustomModelController : Controller
      {
          public IActionResult Index()
          {
              return View();
          }
          [HttpPost]
          public IActionResult Test(TestCustomModel model)
          {
              if (ModelState.IsValid)
              {
  
              }
              return RedirectToAction("Index");
          }
      }

  View

  @model DailyCoreMVCDemo.Models.TestCustomModel
  <form asp-controller="CustomModel" asp-action="Test" method="post">
      <input asp-for="Status" />
      <span asp-validation-for="Status"></span>
      <input type="submit" value="test" />
  </form>
  @section scripts{
      <script src="~/lib/jquery-validation/dist/jquery.validate.min.js"></script>
      <script src="~/lib/jquery-validation-unobtrusive/jquery.validate.unobtrusive.min.js"></script>
  }

  Here is the result. 

  

  Best Regards,

  YihuiSun

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• • Reply
  vkagrawal

  Member

  7 Points

  75 Posts

  Re: Show model property name in custom validation

  Mar 01, 2021 06:01 PM|vkagrawal|LINK

  Hi YihuiSun, 

  Thanks for the direct and detailed explanation. It worked straight away. 
  I just made a change to get the Display attribute property (in case it can have other name than actual property name and can have spaces)

  Instead of

  String.Format(ErrorMessageString,context.ModelMetadata.Name));

  in client side code, I used 

  String.Format(ErrorMessageString, context.ModelMetadata.GetDisplayName());

  Same thing for service side validation message, instead of

  ErrorMessage = String.Format(ErrorMessageString,validationContext.MemberName);

  I used

  ErrorMessage = String.Format(ErrorMessageString, validationContext.DisplayName);

  Rest everything worked fine as expected.

  Thanks!