Is it valid to replace DataAnnotationsModelMetadat

问题:

We are currently building a mid-sized intranet application using MVC3. One requirement is the possibility to change and translate field names and labels on the fly. We are currently using extended versions of ViewPage, ViewMasterPage and ViewUserControl enriched by an translation helper injected by spring.net to achieve this requirement.

This solution solves all requirements except MVC features that rely on ModelMetadata (e.g. LabelFor). My first thought was that there should be an extension point to replace the current implementation. Luckily the MVC team build ModelMetadataProviders in a way that I can inject a custom translation aware DataAnnotationsModelMetadataProvider.

protected override ModelMetadata CreateMetadata( IEnumerable<Attribute> attributes, Type containerType, Func<object> modelAccessor, Type modelType, string propertyName )
{
  // Call the base method and obtain a metadata object.
  var metadata = base.CreateMetadata( attributes, containerType, modelAccessor, modelType, propertyName );

  if( containerType != null )
  {
    // Obtain informations to query the translator.
    var objectName = containerType.FullName;
    var displayName = metadata.GetDisplayName();

    // Query the translator.
    var translatedDisplayName = Translator.Translate( objectName, displayName );

    // Update the metadata.
    metadata.DisplayName = translatedDisplayName;
  }

  return metadata;
}

I'm using the containerType and GetDisplayName() as key to obtain a translation from a translation contributor (that uses caching, does not degrade performance), then calling base and change the returned ModelMetadata by updating the DisplayName property before returning it.

What makes me unconfident about this solution is that I can't predict what side effects I have to expect? Or if there is a better, proper solution?

回答1:

Yes, this is the valid usage.

Make sure you derive from DataAnnotationsModelMetadataProvider as you do to reuse all the features it provides.

You can also handle more custom attributes here - you can decorate your model with your own custom attributes and then update ModelMetadata based on them.