How do I populate a dropdownlist with enum values?

Question

I have an enum for one of the properties of my view-model. I want to display a drop-down list that contains all the values of the enum. I can get this to work with the following code.

What I'm wondering is whether there is a simple way to convert from an enum to an IEnumerable? I can do it manually as in the following example, but when I add a new enum value the code breaks. I imagine that I can do it via reflection as per this example, but but are there other ways to do this?

public enum Currencies
{
  CAD, USD, EUR
}

public ViewModel
{
  [Required]
  public Currencies SelectedCurrency {get; set;}

  public SelectList Currencies
  {
    List<Currencies> c = new List<Currencies>();
    c.Add(Currencies.CAD);
    c.Add(Currencies.USD);
    c.Add(Currencies.EUR);

    return new SelectList(c);
  }
}

Answer 1

I'm using a helper that i found here to populate my SelectLists with a generic enum type, i did a little modification to add the selected value though, here's how it looks like :

public static SelectList ToSelectList<T>(this T enumeration, string selected)
{
    var source = Enum.GetValues(typeof(T));

    var items = new Dictionary<object, string>();

    var displayAttributeType = typeof(DisplayAttribute);

    foreach (var value in source)
    {
        FieldInfo field = value.GetType().GetField(value.ToString());

        DisplayAttribute attrs = (DisplayAttribute)field.
                      GetCustomAttributes(displayAttributeType, false).FirstOrDefault()

        items.Add(value, attrs != null ? attrs.GetName() : value.ToString());
    }

    return new SelectList(items, "Key", "Value", selected);
}

The nice thing about it is that it reads the DisplayAttribute as the title rather than the enum name. (if your enums contain spaces or you need localization then it makes your life much easier)

So you will need to add the Display attirubete to your enums like this :

public enum User_Status
{
    [Display(Name = "Waiting Activation")]
    Pending,    // User Account Is Pending. Can Login / Can't participate

    [Display(Name = "Activated" )]
    Active,                // User Account Is Active. Can Logon

    [Display(Name = "Disabled" )]
    Disabled,          // User Account Is Diabled. Can't Login
}

and this is how you use them in your views.

<%: Html.DropDownList("ChangeStatus" , ListExtensions.ToSelectList(Model.statusType, user.Status))%>

Model.statusType is just an enum object of type User_Status.

That's it , no more SelectLists in your ViewModels. In my example I'm refrencing an enum in my ViewModel but you can Refrence the enum type directly in your view though. I'm just doing it to make everything clean and nice.

Hope that was helpful.

Answer 2

Look at Enum.GetNames(typeof(Currencies))

Answer 3

I am very late on this one but I just found a really cool way to do this with one line of code, if you are happy to add the Unconstrained Melody NuGet package (a nice, small library from Jon Skeet).

This solution is better because:

1. It ensures (with generic type constraints) that the value really is an enum value (due to Unconstrained Melody)
2. It avoids unnecessary boxing (due to Unconstrained Melody)
3. It caches all the descriptions to avoid using reflection on every call (due to Unconstrained Melody)
4. It is less code than the other solutions!

So, here are the steps to get this working:

1. In Package Manager Console, "Install-Package UnconstrainedMelody"

2. Add a property on your model like so:

   //Replace "YourEnum" with the type of your enum
   public IEnumerable<SelectListItem> AllItems
   {
       get
       {
           return Enums.GetValues<YourEnum>().Select(enumValue => new SelectListItem { Value = enumValue.ToString(), Text = enumValue.GetDescription() });
       }
   }
   

Now that you have the List of SelectListItem exposed on your model, you can use the @Html.DropDownList or @Html.DropDownListFor using this property as the source.