Use Enum Values in DropDownListFor

Question

This is my ViewModel:

public class EntityViewModel
{
    [Required(ErrorMessage = "Title is required")]
    [StringLength(255)]
    [DisplayName("Title")]
    public string Title { get; set; }
    [Required(ErrorMessage = "Description is required")]
    [DisplayName("Description")]
    public string Description { get; set; }
    [Required]
    public DateTime StartTime { get; set; }
    [Required]
    public DateTime EndTime { get; set; }

    [Required]
    public Decimal InstantSellingPrice { get; set; }
    public Nullable<Decimal> ShippingPrice { get; set; }
    public Int64 Views { get; set; }

    public Int32 UserId { get; set; }

    public int RegionId { get; set; }

    public short SelectCategoryId { get; set; }
    public SelectList Categories { get; set; }

    public IEnumerable<HttpPostedFileBase> Files { get; set; }

    public Condition? Condition { get; set; }
}

public enum Condition
{
    New=1,
    Used=2
}

This is my Create Action in my Controller:

public ActionResult Create()
{
    ViewBag.DropDownList = ReUzze.Helpers.EnumHelper.SelectListFor<Condition>();

    var model = new ReUzze.Models.EntityViewModel
    {
        Categories = new SelectList(this.UnitOfWork.CategoryRepository.Get(), "Id", "Name")
    };
    return View(model);
  }

In my Create View:

<div class="form-group">
    @Html.LabelFor(model => model.Condition)
    @Html.DropDownListFor(model => model.Condition, ViewBag.DropDownList as SelectList, null)
</div>

I am using the Enumhelper that you can find here.

But now I always get this error in my Create View on this rule:

@Html.DropDownListFor(model => model.Condition, ViewBag.DropDownList as SelectList, null)

The error:

Error 1 The call is ambiguous between the following methods or properties: 'System.Web.Mvc.Html.SelectExtensions.DropDownListFor(System.Web.Mvc.HtmlHelper, System.Linq.Expressions.Expression>, System.Collections.Generic.IEnumerable, string)' and 'System.Web.Mvc.Html.SelectExtensions.DropDownListFor(System.Web.Mvc.HtmlHelper, System.Linq.Expressions.Expression>, System.Collections.Generic.IEnumerable, System.Collections.Generic.IDictionary)' c:\Users\Niels\Documents\Visual Studio 2012\Projects\ReUzze\ReUzze\Views\Entity\Create.cshtml 57 30 ReUzze

Khalid Abuhakmeh · Accepted Answer · 2013-12-19 15:14:34Z

1

I use code like this usually.

public static class Enums {

    public static IList<SelectListItem> SelectListOf<TEnum>(bool empty = false)
    {
        var type = typeof(TEnum);
        if (type.IsEnum)
        {
            var list = Enum.GetValues(type)
                .Cast<TEnum>()
                .OrderBy(x => x)
                .Select(x => new SelectListItem { Text = GetDescription(x), Value = x.ToString() })
                .ToList();

            if (empty)
            {
                list.Insert(0, new SelectListItem());
            }

            return list;

        }

        return new List<SelectListItem>();
    }

    private static string GetDescription(object enumerator)
    {
        try
        {
            //get the enumerator type
            Type type = enumerator.GetType();

            //get the member info
            MemberInfo[] memberInfo = type.GetMember(enumerator.ToString());

            //if there is member information
            if (memberInfo != null && memberInfo.Length > 0)
            {
                //we default to the first member info, as it's for the specific enum value
                object[] attributes = memberInfo[0].GetCustomAttributes(typeof(DescriptionAttribute), false);

                //return the description if it's found
                if (attributes != null && attributes.Length > 0)
                    return ((DescriptionAttribute)attributes[0]).Description;
            }

            //if there's no description, return the string value of the enum
            return enumerator.ToString();
        }
        catch (Exception e)
        {
            return string.Empty;
        }
    }

}

Then you can use it like this:

Conditions = Enums.SelectListOf<Condition>();

answered Dec 19, 2013 at 15:14

Khalid Abuhakmeh

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2 Comments

nielsv Over a year ago

Could you give a little bit more info? Because I don't understand this.. Do I use this in my Model?

Khalid Abuhakmeh Over a year ago

Yes you would use it in the constructor of your viewmodel or you could use it directly in your view.

NinjaNye · Accepted Answer · 2013-12-19 16:15:38Z

1

Check out my blog post on this very subject.

http://jnye.co/Posts/4/creating-a-dropdown-list-from-an-enum-in-mvc-and-c%23

Here is an enum helper I use that turns an enum into a select list. Note: If the enum has a description (using the DescriptionAttribute) it will use that as its display text

public static class EnumHelper
{
    // Get the value of the description attribute if the   
    // enum has one, otherwise use the value.  
    public static string GetDescription<TEnum>(this TEnum value)
    {
        var fi = value.GetType().GetField(value.ToString());

        if (fi != null)
        {
            var attributes = (DescriptionAttribute[])fi.GetCustomAttributes(typeof(DescriptionAttribute), false);

            if (attributes.Length > 0)
            {
                return attributes[0].Description;
            }
        }

        return value.ToString();
    }

    /// <summary>
    /// Build a select list for an enum
    /// </summary>
    public static SelectList SelectListFor<T>() where T : struct
    {
        Type t = typeof(T);
        return !t.IsEnum ? null
                         : new SelectList(BuildSelectListItems(t), "Value", "Text");
    }

    /// <summary>
    /// Build a select list for an enum with a particular value selected 
    /// </summary>
    public static SelectList SelectListFor<T>(T selected) where T : struct
    {
        Type t = typeof(T);
        return !t.IsEnum ? null
                         : new SelectList(BuildSelectListItems(t), "Value", "Text", selected.ToString());
    }

    private static IEnumerable<SelectListItem> BuildSelectListItems(Type t)
    {
        return Enum.GetValues(t)
                   .Cast<Enum>()
                   .Select(e => new SelectListItem { Value = e.ToString(), Text = e.GetDescription() });
    }
}

Once you have this helper class in place you can do the following.

In your controller:

//If you don't have an enum value use the type
ViewBag.DropDownList = EnumHelper.SelectListFor<MyEnum>();

//If you do have an enum value use the value (the value will be marked as selected)    
ViewBag.DropDownList = EnumHelper.SelectListFor(MyEnum.MyEnumValue);

In your View:

@Html.DropDownList("DropDownList")
@* OR *@
@Html.DropDownListFor(m => m.Property, ViewBag.DropDownList as SelectList, null)

answered Dec 19, 2013 at 16:15

NinjaNye

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5 Comments

nielsv Over a year ago

Thanks, how is the Propery defined in the Model?

NinjaNye Over a year ago

Yeah, 'Property' is the property of the viewmodel you are creating a drop down list for. It also provides the selected value

nielsv Over a year ago

Like this: public int ConditionId { get; set; } ?? When I do this I get a huge error

nielsv Over a year ago

Updated my begin post for more clarity.

NinjaNye Over a year ago

remove the last null parameter from the DropDownListFor or replace is with the string of the value you want selected

Neel · Accepted Answer · 2013-12-19 16:13:01Z

0

if you want a quick workaround just for this one view you can do something like this. Although Khalid's approach is recommended.

 <select id = 'myenumdropdown' class='something'>

    @foreach(var item in Enum.GetValues(typeof('yourenumtype')))
    {
      <option value=item.ToHashCode()>item.ToString()</option>
    }

 </select>

answered Dec 19, 2013 at 16:13

Neel

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