In my last post, I talked bout creating a custom class inheriting from System.ComponentModel.DisplayNameAttribute to retrieve display names from resource files:

        [LocalizedDisplayName("RememberMe")]
        public bool RememberMe { get; set; }

That’s a lot of work to put an attribute on all of my model properties though. It would be nice if I could intercept the ASP.NET MVC code that analyzes the model metadata to retrieve display names to make it automatically get localized text from my resource files. That way, I could just set up resource file entries where the keys are the property names, and not have to put attributes on all of my properties.

That’s done by creating a custom class inheriting from System.Web.Mvc.DataAnnotationsModelMetadataProvider:

   1:      public class LocalizedDataAnnotationsModelMetadataProvider :

   2:          DataAnnotationsModelMetadataProvider

   3:      {

   4:          protected override ModelMetadata CreateMetadata(

   5:              IEnumerable<Attribute> attributes, 

   6:              Type containerType, 

   7:              Func<object> modelAccessor, 

   8:              Type modelType, 

   9:              string propertyName)

  10:          {

  11:              var meta = base.CreateMetadata

  12:                  (attributes, containerType, modelAccessor, modelType, propertyName);

  13:   

  14:              if (string.IsNullOrEmpty(propertyName)) 

  15:                  return meta;

  16:   

  17:              if (meta.DisplayName == null)

  18:                  GetLocalizedDisplayName(meta, propertyName);

  19:   

  20:              if (string.IsNullOrEmpty(meta.DisplayName))

  21:                  meta.DisplayName = string.Format("[[{0}]]", propertyName);

  22:   

  23:              return meta;

  24:          }

  25:   

  26:          private static void GetLocalizedDisplayName(ModelMetadata meta, string propertyName)

  27:          {

  28:              ResourceManager resourceManager = MyResource.ResourceManager;

  29:              CultureInfo culture = Thread.CurrentThread.CurrentUICulture;

  30:   

  31:              meta.DisplayName = resourceManager.GetString(propertyName, culture);

  32:          }

  33:      }

Line 11 calls the base CreateMetadata method.

Line 17 checks whether the metadata DisplayName property has already been populated by a DisplayNameAttribute (or my LocalizedDisplayNameAttribute). If so, it respects that and doesn’t use my custom localized text lookup.

The GetLocalizedDisplayName method checks for the property name as a resource file key. If found, it uses the localized text from the resource files.

If the key is not found in the resource file, as with my LocalizedDisplayNameAttribute, I return a formatted string containing the property name (e.g. “[[RememberMe]]”) so I can tell by looking at my web pages which resource keys I haven’t defined yet.

It’s hooked up with this code in the Application_Start method of Global.asax:

    ModelMetadataProviders.Current = new LocalizedDataAnnotationsModelMetadataProvider();