我在我的模型中有一个属性叫做Promotion,它的类型是一个标志enum叫做UserPromotion。枚举成员的显示属性设置如下:

[Flags]
public enum UserPromotion
{
    None = 0x0,

    [Display(Name = "Send Job Offers By Mail")]
    SendJobOffersByMail = 0x1,

    [Display(Name = "Send Job Offers By Sms")]
    SendJobOffersBySms = 0x2,

    [Display(Name = "Send Other Stuff By Sms")]
    SendPromotionalBySms = 0x4,

    [Display(Name = "Send Other Stuff By Mail")]
    SendPromotionalByMail = 0x8
}

现在我想要能够在我的视图中创建一个ul来显示我的Promotion属性的选定值。这就是我到目前为止所做的但问题是,我如何在这里获得显示名称?

<ul>
    @foreach (int aPromotion in @Enum.GetValues(typeof(UserPromotion)))
    {
        var currentPromotion = (int)Model.JobSeeker.Promotion;
        if ((currentPromotion & aPromotion) == aPromotion)
        {
        <li>Here I don't know how to get the display attribute of "currentPromotion".</li>
        }
    }
</ul>

当前回答

你需要使用一些反射来访问该属性:

var type = typeof(UserPromotion);
var member = type.GetMember(Model.JobSeeker.Promotion.ToString());
var attributes = member[0].GetCustomAttributes(typeof(DisplayAttribute), false);
var name = ((DisplayAttribute)attributes[0]).Name;

我建议将此方法包装在扩展方法中,或者在视图模型中执行此操作。

其他回答

一行-流畅的语法

public static class Extensions
{
    /// <summary>
    ///     A generic extension method that aids in reflecting 
    ///     and retrieving any attribute that is applied to an `Enum`.
    /// </summary>
    public static TAttribute GetAttribute<TAttribute>(this Enum enumValue) 
            where TAttribute : Attribute
    {
        return enumValue.GetType()
                        .GetMember(enumValue.ToString())
                        .First()
                        .GetCustomAttribute<TAttribute>();
    }
}

例子

public enum Season 
{
   [Display(Name = "It's autumn")]
   Autumn,

   [Display(Name = "It's winter")]
   Winter,

   [Display(Name = "It's spring")]
   Spring,

   [Display(Name = "It's summer")]
   Summer
}

public class Foo 
{
    public Season Season = Season.Summer;

    public void DisplayName()
    {
        var seasonDisplayName = Season.GetAttribute<DisplayAttribute>();
        Console.WriteLine("Which season is it?");
        Console.WriteLine (seasonDisplayName.Name);
    } 
}

输出

现在是哪个季节? 现在是夏天

使用MVC5你可以使用:

public enum UserPromotion
{
   None = 0x0,

   [Display(Name = "Send Job Offers By Mail")]
   SendJobOffersByMail = 0x1,

   [Display(Name = "Send Job Offers By Sms")]
   SendJobOffersBySms = 0x2,

   [Display(Name = "Send Other Stuff By Sms")]
   SendPromotionalBySms = 0x4,

   [Display(Name = "Send Other Stuff By Mail")]
   SendPromotionalByMail = 0x8
}

然后,如果你想创建一个下拉选择器,你可以使用:

@Html.EnumDropdownListFor(expression: model => model.PromotionSelector, optionLabel: "Select") 
<ul>
    @foreach (int aPromotion in @Enum.GetValues(typeof(UserPromotion)))
    {
        var currentPromotion = (int)Model.JobSeeker.Promotion;
        if ((currentPromotion & aPromotion) == aPromotion)
        {
        <li>@Html.DisplayFor(e => currentPromotion)</li>
        }
    }
</ul>

有了Core 2.1,

public static string GetDisplayName(Enum enumValue)
{
  return enumValue.GetType()?
 .GetMember(enumValue.ToString())?[0]?
 .GetCustomAttribute<DisplayAttribute>()?
 .Name;
}

ASP。Net Core 3.0,这对我很有用(归功于之前的回答)。

我的Enum类:

using System;
using System.Linq;
using System.ComponentModel.DataAnnotations;
using System.Reflection;

public class Enums
{
    public enum Duration
    { 
        [Display(Name = "1 Hour")]
        OneHour,
        [Display(Name = "1 Day")]
        OneDay
    }

    // Helper method to display the name of the enum values.
    public static string GetDisplayName(Enum value)
    {
        return value.GetType()?
       .GetMember(value.ToString())?.First()?
       .GetCustomAttribute<DisplayAttribute>()?
       .Name;
    }
}

我的视图模型类:

public class MyViewModel
{
    public Duration Duration { get; set; }
}

显示标签和下拉列表的剃刀视图示例。注意下拉列表不需要helper方法:

@model IEnumerable<MyViewModel> 

@foreach (var item in Model)
{
    <label asp-for="@item.Duration">@Enums.GetDisplayName(item.Duration)</label>
    <div class="form-group">
        <label asp-for="@item.Duration" class="control-label">Select Duration</label>
        <select asp-for="@item.Duration" class="form-control"
            asp-items="Html.GetEnumSelectList<Enums.Duration>()">
        </select>
    </div>
}