Generating better default DisplayNames from Models in ASP.NET MVC using ModelMetadataProvider

Using the scaffolding in MVC makes it easy to knock up CRUD applications without too much difficulty. Typically you end up with something like this – note the PascalCase field names taken straight from the model generated by Html.LabelFor:

camelcase before

So now the obvious thing is to add DisplayName attributes metadata to your model, for example:

[DisplayName("Assigned To")]
public int AssignedToId { get; set; }

[DisplayName("Customer Name")]
public string CustomerName { get; set; }

Meh, donkey work. In most cases it just needs better default labels in the absence of explicit DisplayName annotations. Nine times out of ten field names such as AssignedToId and CustomerName would be simply expanded to Assigned To and Customer Name. (Of course, they don’t do this out of the box because these simple rules wouldn’t hold true for all languages.)

In MVC you can hook into the metadata discovery/generation process by implementing a ModelMetadataProvider, the default one of which is the DataAnnotationsModelMetadataProvider. So all I did was inherit from the latter and override the GetMetadataForProperty method and if no DisplayName has been specified on the model, create one based on the model’s camel-cased property name.

class MyFabulousModelMetadataProvider : DataAnnotationsModelMetadataProvider
{
   // Uppercase followed by lowercase but not on existing word boundary (eg. the start)
   Regex _camelCaseRegex = new Regex(@"Bp{Lu}p{Ll}", RegexOptions.Compiled);

   // Creates a nice DisplayName from the model’s property name if one hasn't been specified
   protected override ModelMetadata GetMetadataForProperty(
      Func<object> modelAccessor,
      Type containerType,
      PropertyDescriptor propertyDescriptor)
   {
      ModelMetadata metadata = base.GetMetadataForProperty(modelAccessor, containerType, propertyDescriptor);

      if (metadata.DisplayName == null)
         metadata.DisplayName = displayNameFromCamelCase(metadata.GetDisplayName());

      return metadata;
   }

   string displayNameFromCamelCase(string name)
   {
      name = _camelCaseRegex.Replace(name, " $0");
      if (name.EndsWith(" Id"))
          name = name.Substring(0, name.Length - 3);
      return name;
   }
}

Hook the provider up in Application_Start by assigning an instance of it to ModelMetadataProviders.Current.

It’s pretty effective I think:

camelcase after

Anything that isn’t quite right can be overridden simply my explicitly adding DisplayNames to the model.

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