MyModelMetadataProvider

So I was tired of not having any inheritance on Attributes in Mvc for scaffolding, column order, display names and the rest. Here's some code to Allow an attribute called ParentsAttribute to allow you to inject parental metadata for another class that Mvc's DisplayFor will listen to.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Web;
using System.Web.Mvc;

namespace MyMvc.Models
{

  public class ParentsAttribute:Attribute
  {
    public Type[] Values { get; set; }
    public ParentsAttribute(params Type[] parents)
    {
      Values = parents;
    }
  }


  public class MyModelMetadataProvider:DataAnnotationsModelMetadataProvider
  {

    protected override ModelMetadata CreateMetadata(IEnumerable<Attribute> attributes, Type containerType, Func<object> modelAccessor, Type modelType, string propertyName)
    {
      //called once for each property of the viewmodel

      var attrs =attributes.ToArray(); // for possible multiple enumeration
      
      var modelMetadata=base.CreateMetadata(attrs, containerType, modelAccessor, modelType, propertyName);

      if (containerType == null) return modelMetadata;
      var parents =(ParentsAttribute) containerType.GetCustomAttributes(typeof(ParentsAttribute),false).FirstOrDefault(); //search all parents for display attributes that we can inherit
      if(parents==null)
        return modelMetadata;

      var props = from metdataParents in parents.Values
                  from mProp in metdataParents.GetProperties()
              where mProp.CustomAttributes.Any() && mProp.Name == propertyName
                  select new { parent = metdataParents, mProp };
      var sample=props.ToArray();


      var q = from metdataParents in parents.Values
            from mProp in metdataParents.GetProperties()
            where mProp.CustomAttributes.Any() && mProp.Name == propertyName
            
            let da = mProp.GetCustomAttributes(typeof(DisplayAttribute),true).OfType<DisplayAttribute>().FirstOrDefault()
            let dna = mProp.GetCustomAttributes(typeof(DisplayNameAttribute),true).OfType<DisplayNameAttribute>().FirstOrDefault()
            //don't copy down required, may not be required for the current class or viewmodel
            //let ra = mProp.GetCustomAttributes(typeof(RequiredAttribute), true).OfType<RequiredAttribute>().FirstOrDefault()
            where da !=null || dna !=null
            
              select new { mProp,da,dna };
      foreach (var modifier in q)
      {
        if (modifier.da != null)
        {
          //http://aspnetwebstack.codeplex.com/SourceControl/changeset/view/1b78397f32fc#src/System.Web.Mvc/DataAnnotationsModelMetadataProvider.cs
          if (string.IsNullOrEmpty(modelMetadata.Description)) modelMetadata.Description = modifier.da.GetDescription();
          if (string.IsNullOrEmpty(modelMetadata.ShortDisplayName)) modelMetadata.ShortDisplayName = modifier.da.GetShortName();
          if (string.IsNullOrEmpty(modelMetadata.Watermark)) modelMetadata.Watermark = modifier.da.GetPrompt();
          modelMetadata.Order = modifier.da.GetOrder() ?? modelMetadata.Order;
          if (string.IsNullOrEmpty(modifier.da.GetName()) == false) //only set current object if it is overriding the display
          {
            modelMetadata.DisplayName = modifier.da.GetName();  
          } else if (modifier.dna != null)
          {
            modelMetadata.DisplayName = modifier.dna.DisplayName;
          }
          
        }
        
      }

      return modelMetadata;

    }
  }
}

And don't forget to hook it up in your Global.asax! ModelMetadataProviders.Current = new MyModelMetadataProvider();