Question

I know there is several threads on this topic. I see a lot of solutions but most of them demands the knowledge of which type the enum is. Since Enum by default renders uses the template for string, it’s more difficult to find out the exact type.

Has someone got a complete example on how to solve this?

Edit. Based on Roys suggestion, here’s my code.

HtmlHelpers.cs

public static MvcHtmlString EnumDropDownListFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression) where TModel : class
{
    var type = htmlHelper.ViewData.ModelMetadata.ModelType;
    var inputName = type.Name;
    var value = htmlHelper.ViewData.Model == null ? default(TProperty) : expression.Compile()(htmlHelper.ViewData.Model);
    var selected = value == null ? String.Empty : value.ToString();
    return htmlHelper.DropDownList(inputName, ToSelectList(type, selected));
}

private static IEnumerable<SelectListItem> ToSelectList(Type enumType, string selectedItem)
{
    var items = new List<SelectListItem>();
    foreach (var item in Enum.GetValues(enumType))
    {
        var fi = enumType.GetField(item.ToString());
        var attribute = fi.GetCustomAttributes(typeof(DescriptionAttribute), true).FirstOrDefault();
        var title = attribute == null ? item.ToString() : ((DescriptionAttribute)attribute).Description;
        var listItem = new SelectListItem
        {
            Value = ((int)item).ToString(),
            Text = title,
            Selected = selectedItem == ((int)item).ToString()
        };
        items.Add(listItem);
    }

    return new SelectList(items, "Value", "Text");
}

Viewmodel

public class AddTestForm
{
    [UIHint("Enum")]
    public EnumType Type { get; set; }

    public string Description { get; set; }

public enum EnumType
{
    One = 1,
    Two = 2
}

EditorTemplates/Enum.cshtml

@model object

@Html.EnumDropDownListFor(x => x)

And in views…

@Html.EditorForModel()

The problem now is that I can’t get the enum to fill after the form has been posted.

Answer 1

Your helper generates wrong names to the generated select elements:

<select id="Type_EnumType" name="Type.EnumType">

The DefaultModelBinder uses the name attribute to match the property names. Your helper generated name "Type.EnumType" doesn’t match with the Model property name "Type". To make it work instead of the Type name you need to get the property name from the expression. It’s quite easy with the ExpressionHelper class:

public static MvcHtmlString EnumDropDownListFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression) where TModel : class
{
    ...
    return htmlHelper.DropDownList(ExpressionHelper.GetExpressionText(expression), ToSelectList(type, selected));
}