从 MVC 5.1 EnumDropDownListFor 中排除/删除值

您可以构建一个下拉列表：

@{ // you can put the following in a back-end method and pass through ViewBag
   var selectList = Enum.GetValues(typeof(UserStatus))
                        .Cast<UserStatus>()
                        .Where(e => e != UserStatus.Pending)
                        .Select(e => new SelectListItem 
                            { 
                                Value = ((int)e).ToString(),
                                Text = e.ToString()
                            });
}
@Html.DropDownListFor(m => m.Status, selectList)

@dav_i的答案修改。

这并不完美，但这是我正在使用的。以下是HtmlHelper的扩展。扩展方法看起来像 ASP.NET 中的EnumDropDownListFor，如果有任何应用于 Enum 值，请使用 DisplayAttribute。

/// <summary>
/// Returns an HTML select element for each value in the enumeration that is
/// represented by the specified expression and predicate.
/// </summary>
/// <typeparam name="TModel">The type of the model.</typeparam>
/// <typeparam name="TEnum">The type of the value.</typeparam>
/// <param name="htmlHelper">The HTML helper instance that this method extends.</param>
/// <param name="expression">An expression that identifies the object that contains the properties to display.</param>
/// <param name="optionLabel">The text for a default empty item. This parameter can be null.</param>
/// <param name="predicate">A <see cref="Func{TEnum, bool}"/> to filter the items in the enums.</param>
/// <param name="htmlAttributes">An object that contains the HTML attributes to set for the element.</param>
/// <returns>An HTML select element for each value in the enumeration that is represented by the expression and the predicate.</returns>
/// <exception cref="ArgumentNullException">If expression is null.</exception>
/// <exception cref="ArgumentException">If TEnum is not Enum Type.</exception>
public static MvcHtmlString EnumDropDownListFor<TModel, TEnum>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TEnum>> expression, Func<TEnum, bool> predicate, string optionLabel, object htmlAttributes) where TEnum : struct, IConvertible
{
    if (expression == null)
    {
        throw new ArgumentNullException("expression");
    }
    if (!typeof(TEnum).IsEnum)
    {
        throw new ArgumentException("TEnum");
    }
    
    IList<SelectListItem> selectList = Enum.GetValues(typeof(TEnum))
            .Cast<TEnum>()
            .Where(e => predicate(e))
            .Select(e => new SelectListItem
                {
                    Value = Convert.ToUInt64(e).ToString(),
                    Text = ((Enum)(object)e).GetDisplayName(),
                }).ToList();
    if (!string.IsNullOrEmpty(optionLabel)) {
        selectList.Insert(0, new SelectListItem {
            Text = optionLabel,
        });
    }
    return htmlHelper.DropDownListFor(expression, selectList, htmlAttributes);
}
/// <summary>
/// Gets the name in <see cref="DisplayAttribute"/> of the Enum.
/// </summary>
/// <param name="enumeration">A <see cref="Enum"/> that the method is extended to.</param>
/// <returns>A name string in the <see cref="DisplayAttribute"/> of the Enum.</returns>
public static string GetDisplayName(this Enum enumeration)
{
    Type enumType = enumeration.GetType();
    string enumName = Enum.GetName(enumType, enumeration);
    string displayName = enumName;
    try
    {
        MemberInfo member = enumType.GetMember(enumName)[0];
        object[] attributes = member.GetCustomAttributes(typeof(DisplayAttribute), false);
        DisplayAttribute attribute = (DisplayAttribute)attributes[0];
        displayName = attribute.Name;
        if (attribute.ResourceType != null)
        {
            displayName = attribute.GetName();
        }
    }
    catch { }
    return displayName;
}

例如：

@Html.EnumDropDownListFor(
    model => model.UserStatus,
    (userStatus) => { return userStatus != UserStatus.Active; },
    null,
    htmlAttributes: new { @class = "form-control" })

这将创建一个不带"活动"选项的枚举下拉列表。

循环访问枚举中的值来自己创建下拉列表，并且仅在<option>未挂起时才包含下拉列表。

这是它应该如何工作，但如您所见，我不确定您将使用什么作为选项标签的值或文本。

<select>
foreach (var status in Enum.GetValues(typeof(UserStatus)))
{
    if(status != UserStatus.Pending)
    {
        <option value="status.???">@status.???</option>
    }
}
</select>

我一直在寻找这个问题的答案，因为它与.NET Core MVC有关。 给定以下代码，您可以限制不希望在 UI 中显示的枚举：

<select asp-for="UserStatus" asp-items="@(Html.GetEnumSelectList<UserStatus>().Where(x => x.Value != 0))" class="form-control">
    <option selected="selected" value="">Please select</option>
</select>

希望这有助于其他寻找此答案的人。

下面是 HtmlHelper 的扩展。它与 ASP.NET 中的 EnumDropDownListFor 扩展非常相似，但它按项目显示名称对 SelectListItem 进行排序。它有一个暗示性的名称：SortedEnumDropDownListFor ，因为与原始扩展不冲突。

    /// <summary>
    /// 
    /// </summary>
    /// <typeparam name="TModel">The type of the model.</typeparam>
    /// <typeparam name="TEnum">The type of the value.</typeparam>
    /// <param name="htmlHelper">The HTML helper instance that this method extends.</param>
    /// <param name="expression">An expression that identifies the object that contains the properties to display</param>
    /// <param name="initalValue">The unselected item initial value</param>
    /// <param name="htmlAttributes"></param>
    /// <returns></returns>
    public static MvcHtmlString SortedEnumDropDownListFor<TModel, TEnum>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TEnum>> expression, string initalValue, object htmlAttributes = null)
    {
        ModelMetadata metadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
        Type enumType = GetNonNullableModelType(metadata);
        Type baseEnumType = Enum.GetUnderlyingType(enumType);
        List<SelectListItem> items = new List<SelectListItem>();
        foreach (FieldInfo field in enumType.GetFields(BindingFlags.Static | BindingFlags.GetField | BindingFlags.Public))
        {
            string text = field.Name;
            string value = Convert.ChangeType(field.GetValue(null), baseEnumType).ToString();
            bool selected = field.GetValue(null).Equals(metadata.Model);
            foreach (DisplayAttribute displayAttribute in field.GetCustomAttributes(true).OfType<DisplayAttribute>())
            {
                text = displayAttribute.GetName();
            }
            items.Add(new SelectListItem
            {
                Text = text,
                Value = value,
                Selected = selected
            });
        }
        items = new List<SelectListItem>(items.OrderBy(s => s.Text));
        items.Insert(0, new SelectListItem { Text = initalValue, Value = "" });
        return htmlHelper.DropDownListFor(expression, items, htmlAttributes);
    }        
    private static Type GetNonNullableModelType(ModelMetadata modelMetadata)
    {
        Type realModelType = modelMetadata.ModelType;
        Type underlyingType = Nullable.GetUnderlyingType(realModelType);
        if (underlyingType != null)
        {
            realModelType = underlyingType;
        }
        return realModelType;
    }

如果您不想打扰未选择的项目初始化，只需构建如下所示的重载：

public static MvcHtmlString SortedEnumDropDownListFor<TModel, TEnum>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TEnum>> expression, object htmlAttributes = null)
        {
            MvcHtmlString helper = SortedEnumDropDownListFor(htmlHelper, expression, string.Empty, htmlAttributes);
            return helper;
        }

你很好去。我希望它有所帮助。