Question

我是asp.net MVC的新手。我试图在我的视图页面上使用下拉控件，该页面从枚举中填充。我还想为下拉列表添加自定义描述。我搜索了很多例子，但没有人发布如何在视图页面上填充描述。这是我的代码：

视图模型：

public enum SearchBy
    {
        [Description("SID/PID")]
        SID = 1,
        [Description("Name")]
        Name,
        [Description("Birth Date")]
        DOB,
        [Description("Cause#")]
        Cause
    }

Index.cshtml

<div class="form-horizontal">
    @Html.ValidationSummary(true, "", new { @class = "text-danger" })
    <div class="form-group form-inline">
        @Html.LabelFor(model => model.searchBy, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EnumDropDownListFor(model => model.searchBy, "Search By", htmlAttributes: new { @class = "form-control" })
            @Html.TextBox("searchByVal", null, htmlAttributes: new { @placeholder = "SID / PID ", @class = "form-control" })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.FirstName, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.FirstName, new { htmlAttributes = new { @placeholder = "First Name", @class = "form-control" } })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.LastName, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.LastName, new { htmlAttributes = new { @placeholder = "Last Name", @class = "form-control" } })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.DOB, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.DOB, new { htmlAttributes = new { @placeholder = "Birth Date", @class = "form-control" } })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.CauseNumber, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.CauseNumber, new { htmlAttributes = new { @placeholder = "Cause#", @class = "form-control" } })
        </div>
    </div>

    <div class="form-group">
        <div class="col-md-offset-2 col-md-10">
            <input type="submit" value="Search" class="btn btn-block btn-primary" />
        </div>
    </div>
</div>

它没有填充我的SearchBy枚举中提到的with description字段。看到这里的图像。 http://postimg.org/image/phdxgocj7/ 请帮助我，我犯了错误。谢谢

更新我从Nico那里得到了解决方案。我对此进行了一些研究。我正在使用解决方案更新此帖子，因为它可能对其他人有用，他们是MVC的新手 http://weblogs.asp.net/jongalloway//looking-at-asp-net-mvc-5-1-and-web-api-2-1-part-1-overview-and-enums

谢谢大家。享受编码..

Answer 1

Html帮助器EnumDropDownListFor或EnumDropDownList未考虑Description成员上的enum属性修饰。但是，通过查看源代码：

Enum下拉列表助手： https://aspnetwebstack.codeplex.com/SourceControl/latest#src/System.Web.Mvc/Html/SelectExtensions.cs

Enum Helper Classes： https://aspnetwebstack.codeplex.com/SourceControl/latest#src/System.Web.Mvc/Html/EnumHelper.cs

上面的枚举助手类用于将Enum转换为List<SelectListItem>。从下面的代码：

// Return non-empty name specified in a [Display] attribute for the given field, if any; field's name otherwise
private static string GetDisplayName(FieldInfo field)
{
    DisplayAttribute display = field.GetCustomAttribute<DisplayAttribute>(inherit: false);
    if (display != null)
    {
        string name = display.GetName();
        if (!String.IsNullOrEmpty(name))
        {
            return name;
        }
    }

    return field.Name;
}

您可以在方法GetDisplayName中看到它检查DisplayAttribute成员上是否存在enum。如果display属性存在，则将名称设置为DisplayAttribute.GetName()方法的结果。

将这些放在一起，我们可以修改enum以使用DisplayAttribute代替DescriptionAttribute并将Name属性设置为您希望显示的值。

public enum SearchBy
{
    [Display(Name = "SID/PID")]
    SID = 1,
    [Display(Name = "Name")]
    Name,
    [Display(Name = "Birth Date")]
    DOB,
    [Display(Name = "Cause#")]
    Cause
}

这可以为您提供所需的结果。

enter image description here

希望这有帮助。

Answer 2

鉴于：

public enum MyEnum
{
    [Description("This is the description if my member A")]
    A,
    [Description("This is the description if my member B")]
    B
}

我个人使用这种扩展方法从我的枚举中获取描述：

 public static string GetDescription(this Enum 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();
            }
        }

使用它：

MyEnum.A.GetDescription();

希望得到这个帮助。

Answer 3

我创建了一个尝试不同类型属性的辅助类。我需要它，因为我使用了https://github.com/civicsource/enums和https://silviomoreto.github.io/bootstrap-select/

的引导程序

public static class EnumHelper<T>
    {
        static EnumHelper()
        {
            var enumType = typeof(T);
            if (!enumType.IsEnum) { throw new ArgumentException("Type '" + enumType.Name + "' is not an enum"); }
        }

        public static string GetEnumDescription(T value)
        {
            var fi = typeof(T).GetField(value.ToString());
            var attributes = (DescriptionAttribute[]) fi.GetCustomAttributes(typeof(DescriptionAttribute), false);
            return attributes.Length > 0 ? attributes[0].Description : value.ToString();
        }

        public static IEnumerable<SelectListItem> GetSelectList()
        {
            var groupDictionary = new Dictionary<string, SelectListGroup>();

            var enumType = typeof(T);
            var fields = from field in enumType.GetFields()
                         where field.IsLiteral
                         select field;

            foreach (var field in fields)
            {
                var display = field.GetCustomAttribute<DisplayAttribute>(false);
                var description = field.GetCustomAttribute<DescriptionAttribute>(false);
                var group = field.GetCustomAttribute<CategoryAttribute>(false);

                var text = display?.GetName() ?? display?.GetShortName() ?? display?.GetDescription() ?? display?.GetPrompt() ?? description?.Description ?? field.Name;
                var value = field.Name;
                var groupName = display?.GetGroupName() ?? group?.Category ?? string.Empty;
                if (!groupDictionary.ContainsKey(groupName)) { groupDictionary.Add(groupName, new SelectListGroup { Name = groupName }); }

                yield return new SelectListItem
                {
                    Text = text,
                    Value = value,
                    Group = groupDictionary[groupName],
                };
            }
        }
    }

你称之为：

<div class="form-group">
   @Html.LabelFor(model => model.Address.State, htmlAttributes: new { @class = "control-label col-md-2" })
   <div class="col-sm-4">
      @Html.DropDownListFor(model => model.Address.State, EnumHelper<StateProvince>.GetSelectList(), new { @class = "selectpicker show-menu-arrow", data_live_search = "true" })
      @Html.ValidationMessageFor(model => model.Address.State, "", new { @class = "text-danger" })
   </div>
</div>

Answer 4

如果您使用的是.Net Framework 4.0或更高版本，则无需创建帮助器类。

您可以将Display属性与EnumDropDownListFor一起使用

public enum SearchBy
{
    [Display(Name = "SID/PID")]
    SID = 1,
    [Display(Name = "Name")]
    Name,
    [Display(Name = "Birth Date")]
    DOB,
    [Display(Name = "Cause#")]
    Cause
}

在您看来：

@Html.EnumDropDownListFor(model => model.SearchBy, "Search By", new { @class = "form-control" })

Microsoft文档：

https://docs.microsoft.com/en-us/dotnet/api/system.componentmodel.dataannotations.displayattribute?view=netframework-4.8

如何在asp.net mvc中使用带有DescriptionAttribute的枚举

4 个答案: