ASP.NET MVC: Creating localized DropDownLists for enums

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Web;
using System.Text;
using System.Web.Mvc;
using System.Web.Mvc.Html;

using System.Diagnostics.CodeAnalysis;
using System.Reflection;
using System.Resources;

using MvcEnumDropDownList.Infrastructure;

namespace MvcEnumDropDownList.Helpers
{
	/// <summary>
	/// ASP.NET MVC - Creating a DropDownList helper for enums
	/// </summary>
	/// <see cref="http://blogs.msdn.com/b/stuartleeks/archive/2010/05/21/asp-net-mvc-creating-a-dropdownlist-helper-for-enums.aspx"/>
	public static partial class DropDownList
	{
		public static MvcHtmlString EnumDropDownList<TEnum>(this HtmlHelper htmlHelper, string name)
		{
			return EnumDropDownList<TEnum>(htmlHelper, name, null /* optionLabel */, null /* htmlAttributes */);
		}

		public static MvcHtmlString EnumDropDownList<TEnum>(this HtmlHelper htmlHelper, string name, string optionLabel)
		{
			return EnumDropDownList<TEnum>(htmlHelper, name, optionLabel, null /* htmlAttributes */);
		}

		public static MvcHtmlString EnumDropDownList<TEnum>(this HtmlHelper htmlHelper, string name, IEnumerable<SelectListItem> selectList)
		{
			return EnumDropDownList<TEnum>(htmlHelper, name, null /* optionLabel */, null /* htmlAttributes */);
		}

		public static MvcHtmlString EnumDropDownList<TEnum>(this HtmlHelper htmlHelper, string name, object htmlAttributes)
		{
			return EnumDropDownList<TEnum>(htmlHelper, name, null /* optionLabel */, HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes));
		}

		public static MvcHtmlString EnumDropDownList<TEnum>(this HtmlHelper htmlHelper, string name, IDictionary<string, object> htmlAttributes)
		{
			return EnumDropDownList<TEnum>(htmlHelper, name, null /* optionLabel */, htmlAttributes);
		}

		public static MvcHtmlString EnumDropDownList<TEnum>(this HtmlHelper htmlHelper, string name, string optionLabel, object htmlAttributes)
		{
			return EnumDropDownList<TEnum>(htmlHelper, name, optionLabel, HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes));
		}

		public static MvcHtmlString EnumDropDownList<TEnum>(this HtmlHelper htmlHelper, string name, string optionLabel, IDictionary<string, object> htmlAttributes)
		{
			IEnumerable<SelectListItem> selectList = GetSelectListItems<TEnum>(null);
			return htmlHelper.DropDownList(name, selectList, optionLabel, htmlAttributes);
		}



		//
		//
		// Specifying Resource type
		//
		//

		public static MvcHtmlString EnumDropDownList<TEnum, TResource>(this HtmlHelper htmlHelper, string name)
		{
			return EnumDropDownList<TEnum, TResource>(htmlHelper, name, null /* optionLabel */, null /* htmlAttributes */);
		}

		public static MvcHtmlString EnumDropDownList<TEnum, TResource>(this HtmlHelper htmlHelper, string name, string optionLabel)
		{
			return EnumDropDownList<TEnum, TResource>(htmlHelper, name, optionLabel, null /* htmlAttributes */);
		}

		public static MvcHtmlString EnumDropDownList<TEnum, TResource>(this HtmlHelper htmlHelper, string name, object htmlAttributes)
		{
			return EnumDropDownList<TEnum, TResource>(htmlHelper, name, null /* optionLabel */, HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes));
		}

		public static MvcHtmlString EnumDropDownList<TEnum, TResource>(this HtmlHelper htmlHelper, string name, IDictionary<string, object> htmlAttributes)
		{
			return EnumDropDownList<TEnum, TResource>(htmlHelper, name, null /* optionLabel */, htmlAttributes);
		}

		public static MvcHtmlString EnumDropDownList<TEnum, TResource>(this HtmlHelper htmlHelper, string name, string optionLabel, object htmlAttributes)
		{
			return EnumDropDownList<TEnum, TResource>(htmlHelper, name, optionLabel, HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes));
		}

		public static MvcHtmlString EnumDropDownList<TEnum, TResource>(this HtmlHelper htmlHelper, string name, string optionLabel, IDictionary<string, object> htmlAttributes)
		{
			IEnumerable<SelectListItem> selectList = GetSelectListItems<TEnum>(typeof(TResource));
			return htmlHelper.DropDownList(name, selectList, optionLabel, htmlAttributes);
		}

	

		#region Private methods 

		/// <summary>
		/// Gets the select list items.
		/// </summary>
		/// <typeparam name="TEnum">The type of the enum.</typeparam>
		/// <param name="selectList">The select list.</param>
		/// <param name="resourceType">Type of the resource.</param>
		/// <returns></returns>
		private static IEnumerable<SelectListItem> GetSelectListItems<TEnum>(Type resourceType)
		{
			bool isEnum = EnumHelper.IsEnum<TEnum>();

			if(!isEnum)
				throw new ArgumentException("TEnum must be an enumerated type");

			IEnumerable<SelectListItem> values = EnumHelper.GetEnumValues<TEnum>(resourceType).Select(x =>
				new SelectListItem {
					Text = x.Value,
					Value = Convert.ToInt32(x.Key).ToString()
				}
			);

			return values;
		}

		private static Type GetNonNullableModelType(ModelMetadata modelMetadata)
		{
			Type realModelType = modelMetadata.ModelType;

			Type underlyingType = Nullable.GetUnderlyingType(realModelType);
			if(underlyingType != null)
			{
				realModelType = underlyingType;
			}
			return realModelType;
		}

		#endregion
	}
}