Create custom display attribute using or inherits DisplayAttribute in ASP.NET MVC

Question

I want to use DisplayAttribute with Name property.

The problem is that class is sealed and I cannot inherits it to override some methods.

Why I want this ?

I want to pass some a code in order to translate strings to Name property. And add one property for language.

Something like:

[MyDisplay(Code = TRANSLATION_CODE, Language = "FR-FR")]
public string Fr { get; set; }

And inside MyDisplayAttribute, I want to do like:

public class MyDisplayAttribute: DisplayAttribute // it won't work the inherits
{
     public int Code { get; set; }
     public string Language { get; set; }

    // somewhere, I don't know what method
    // I want to assing `Name = GetTranslation(Code, Language);`
}

There is another way to do that ?

---

UPDATE

I tried also this:

public class MyDisplayAttribute : DisplayNameAttribute
   {
      private int _code;
      private string _language;

      public MyDisplayAttribute( int code, string language )
         : base( language )
      {
         _code = code;
         _language = language;
      }

      public override string DisplayName
      {
         get
         {
            // here come LanguageTranslatorManager
            if ( _code == 1 && _language == "en" ) {
               return "test";
            }

            return base.DisplayName;
         }
      }
   }

and in model:

  [MyDisplay( 1, "en" )]
  public string Test
  {
     get;
     set;
  }

I'm expecting to display test in view, but doesn't ! Where is my mistake ?

Answer 1

In order to set a specific display name for your property, you need to set the metadata property DisplayName. If you need to write custom attributes, you need to make sure that you create a custom metadata provider. Inside you need to set the DisplayName of your property, based on the values provided.

public class CustomModelMetadataProvider : DataAnnotationsModelMetadataProvider
{
    protected override ModelMetadata CreateMetadata(IEnumerable<Attribute> attributes,
          Type containerType, Func<object> modelAccessor, 
          Type modelType, string propertyName)
    { 
         var modelMetadata = base.CreateMetadata(attributes, containerType, 
                 modelAccessor, modelType, propertyName);

         if (attributes.OfType<MyDisplay>().ToList().Count > 0)
         {
              modelMetadata.DisplayName = GetValueFromLocalizationAttribute(attributes.OfType<MyDisplay>().ToList()[0]);
         }

         return modelMetadata;
    }

    private string GetValueFromLocalizationAttribute(MyDisplay attribute)
    {
          return computedValueBasedOnCodeAndLanguage;
    }
}

Answer 2

You are doing it wrong. The DisplayAttribute already supports 'translations' using the built-in .net internationalization

 [Display(Name = "property_name", ResourceType = typeof(MyResources))]

Only if that's not enough you should create your own attribute, but not deriving from Display.

Edit:

The DisplayAttribute is a sealed class, so there is no way to inherit from it.