Wednesday, March 30, 2016

@Html.EnumDropDownListFor in MVC

For MVC v5.1 use Html.EnumDropDownListFor

        @Html.DropDownList("MyType", 
           Html.GetEnumSelectList(typeof(MyType)) , 
           "Select My Type", 
           new { @class = "form-control" })
    

For MVC v5 use EnumHelper

        @Html.DropDownList("MyType", 
           EnumHelper.GetSelectList(typeof(MyType)) , 
           "Select My Type", 
           new { @class = "form-control" })
    

For MVC >5 and lower

I rolled Rune's answer into an extension method:
        namespace MyApp.Common
        {
            public static class MyExtensions{
                public static SelectList ToSelectList(this TEnum enumObj)
                    where TEnum : struct, IComparable, IFormattable, IConvertible
                {
                    var values = from TEnum e in Enum.GetValues(typeof(TEnum))
                        select new { Id = e, Name = e.ToString() };
                    return new SelectList(values, "Id", "Name", enumObj);
                }
            }
        }
    
This allows you to write:
     ViewData["taskStatus"] = task.Status.ToSelectList();
    
by
using MyApp.Common

Alternatively:
Create a custom helper class and use Html.EnumDropDownListFor for all lower version MVC < 5.1 (i.e. 3.x, 4.x, 5.0). Here is the class code:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using System.Web.Mvc;
using System.Web.Mvc.Html;
/// 
/// Class ENUM Helper
/// 
public static class EnumHelper
{
    /// 
    /// The single empty item
    /// 
    private static readonly SelectListItem[] SingleEmptyItem = new[] { new SelectListItem { Text = string.Empty, Value = string.Empty } };
    /// 
    /// Gets the ENUM description.
    /// 
    /// The type of the ENUM.
    /// The value.
    /// ENUM Description
    public static string GetEnumDescription(TEnum value)
    {
        FieldInfo fi = value.GetType().GetField(value.ToString());
        DescriptionAttribute[] attributes = (DescriptionAttribute[])fi.GetCustomAttributes(typeof(DescriptionAttribute), false);
        if ((attributes != null) && (attributes.Length > 0))
        {
            return attributes[0].Description;
        }
        else
        {
            return value.ToString();
        }
    }
    /// 
    /// ENUMS the drop down list for.
    /// 
    /// The type of the model.
    /// The type of the ENUM.
    /// The HTML helper.
    /// The expression.
    /// MVC Html String
    public static MvcHtmlString EnumDropDownListFor(this HtmlHelper htmlHelper, Expression> expression)
    {
        return EnumDropDownListFor(htmlHelper, expression, null);
    }
    /// 
    /// ENUMS the drop down list for.
    /// 
    /// The type of the model.
    /// The type of the ENUM.
    /// The HTML helper.
    /// The expression.
    /// The HTML attributes.
    /// MVC Html String
    public static MvcHtmlString EnumDropDownListFor(this HtmlHelper htmlHelper, Expression> expression, object htmlAttributes)
    {
        ModelMetadata metadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
        Type enumType = GetNonNullableModelType(metadata);
        IEnumerable values = Enum.GetValues(enumType).Cast();
        IEnumerable items = from value in values
                                            select new SelectListItem
                                            {
                                                Text = GetEnumDescription(value),
                                                Value = value.ToString(),
                                                Selected = value.Equals(metadata.Model)
                                            };
        // If the enum is nullable, add an 'empty' item to the collection
        if (metadata.IsNullableValueType)
        {
            items = SingleEmptyItem.Concat(items);
        }
        return htmlHelper.DropDownListFor(expression, items, htmlAttributes);
    }
    /// 
    /// Gets the type of the non null-able model.
    /// 
    /// The model metadata.
    /// real Model Type
    private static Type GetNonNullableModelType(ModelMetadata modelMetadata)
    {
        Type realModelType = modelMetadata.ModelType;
        Type underlyingType = Nullable.GetUnderlyingType(realModelType);
        if (underlyingType != null)
        {
            realModelType = underlyingType;
        }
        return realModelType;
    }
}

Usage:

   @Html.EnumDropDownListFor(model => model.EnumProperty, "Select Enum", new { @class = "form-control", type = "text"})
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