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

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>
}

其他回答

基于之前的答案,我创建了这个舒适的帮助器,以可读的方式支持所有DisplayAttribute属性:

public static class EnumExtensions
    {
        public static DisplayAttributeValues GetDisplayAttributeValues(this Enum enumValue)
        {
            var displayAttribute = enumValue.GetType().GetMember(enumValue.ToString()).First().GetCustomAttribute<DisplayAttribute>();

            return new DisplayAttributeValues(enumValue, displayAttribute);
        }

        public sealed class DisplayAttributeValues
        {
            private readonly Enum enumValue;
            private readonly DisplayAttribute displayAttribute;

            public DisplayAttributeValues(Enum enumValue, DisplayAttribute displayAttribute)
            {
                this.enumValue = enumValue;
                this.displayAttribute = displayAttribute;
            }

            public bool? AutoGenerateField => this.displayAttribute?.GetAutoGenerateField();
            public bool? AutoGenerateFilter => this.displayAttribute?.GetAutoGenerateFilter();
            public int? Order => this.displayAttribute?.GetOrder();
            public string Description => this.displayAttribute != null ? this.displayAttribute.GetDescription() : string.Empty;
            public string GroupName => this.displayAttribute != null ? this.displayAttribute.GetGroupName() : string.Empty;
            public string Name => this.displayAttribute != null ? this.displayAttribute.GetName() : this.enumValue.ToString();
            public string Prompt => this.displayAttribute != null ? this.displayAttribute.GetPrompt() : string.Empty;
            public string ShortName => this.displayAttribute != null ? this.displayAttribute.GetShortName() : this.enumValue.ToString();
        }
    }

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。

我很抱歉这样做,但我不能使用任何其他的答案,也没有时间在评论中争论。

使用c# 6语法。

static class EnumExtensions
{
    /// returns the localized Name, if a [Display(Name="Localised Name")] attribute is applied to the enum member
    /// returns null if there isnt an attribute
    public static string DisplayNameOrEnumName(this Enum value)
    // => value.DisplayNameOrDefault() ?? value.ToString()
    {
        // More efficient form of ^ based on http://stackoverflow.com/a/17034624/11635
        var enumType = value.GetType();
        var enumMemberName = Enum.GetName(enumType, value);
        return enumType
            .GetEnumMemberAttribute<DisplayAttribute>(enumMemberName)
            ?.GetName() // Potentially localized
            ?? enumMemberName; // Or fall back to the enum name
    }

    /// returns the localized Name, if a [Display] attribute is applied to the enum member
    /// returns null if there is no attribute
    public static string DisplayNameOrDefault(this Enum value) =>
        value.GetEnumMemberAttribute<DisplayAttribute>()?.GetName();

    static TAttribute GetEnumMemberAttribute<TAttribute>(this Enum value) where TAttribute : Attribute =>
        value.GetType().GetEnumMemberAttribute<TAttribute>(value.ToString());

    static TAttribute GetEnumMemberAttribute<TAttribute>(this Type enumType, string enumMemberName) where TAttribute : Attribute =>
        enumType.GetMember(enumMemberName).Single().GetCustomAttribute<TAttribute>();
}

基于Todd的答案,建立在Aydin的答案之上,这是一个不需要任何类型参数的泛型扩展方法。

/// <summary>
/// Gets human-readable version of enum.
/// </summary>
/// <returns>effective DisplayAttribute.Name of given enum.</returns>
public static string GetDisplayName<T>(this T enumValue) where T : IComparable, IFormattable, IConvertible // C# 7.3+: where T : struct, Enum
{
    if (!typeof(T).IsEnum) // Not needed in C# 7.3+ with above updated constraint
        throw new ArgumentException("Argument must be of type Enum");

    DisplayAttribute displayAttribute = enumValue.GetType()
                                                 .GetMember(enumValue.ToString())
                                                 .First()
                                                 .GetCustomAttribute<DisplayAttribute>();

    string displayName = displayAttribute?.GetName();

    return displayName ?? enumValue.ToString();
}

我需要这个为我的项目,因为像下面的代码,其中不是每个成员的enum有一个DisplayAttribute,抛出一个异常与Todd的解决方案:

public class MyClass
{
    public enum MyEnum 
    {
        [Display(Name="ONE")]
        One,
        // No DisplayAttribute
        Two
    }
    public void UseMyEnum()
    {
        MyEnum foo = MyEnum.One;
        MyEnum bar = MyEnum.Two;
        Console.WriteLine(foo.GetDisplayName());
        Console.WriteLine(bar.GetDisplayName());
    }
}
// Output:
//
// ONE
// Two

如果这是一个简单问题的复杂解决方案,请让我知道,但这是我使用的修复。

对于这个问题,我有两个解决方案。

第一个解决方案是从enum中获取显示名称。

public enum CourseLocationTypes
{
    [Display(Name = "On Campus")]
    OnCampus,
    [Display(Name = "Online")]
    Online,
    [Display(Name = "Both")]
    Both
}

public static string DisplayName(this Enum value)
{
    Type enumType = value.GetType();
    string enumValue = Enum.GetName(enumType, value);
    MemberInfo member = enumType.GetMember(enumValue)[0];

    object[] attrs = member.GetCustomAttributes(typeof(DisplayAttribute), false);
    string outString = ((DisplayAttribute)attrs[0]).Name;

    if (((DisplayAttribute)attrs[0]).ResourceType != null)
    {
        outString = ((DisplayAttribute)attrs[0]).GetName();
    }

    return outString;
}
<h3 class="product-title white">@Model.CourseLocationType.DisplayName()</h3>

第二个解决方案是从枚举名称中获取显示名称,但在开发人员语言中它被称为patch。

public static string SplitOnCapitals(this string text)
{
        var r = new Regex(@"
            (?<=[A-Z])(?=[A-Z][a-z]) |
             (?<=[^A-Z])(?=[A-Z]) |
             (?<=[A-Za-z])(?=[^A-Za-z])", RegexOptions.IgnorePatternWhitespace);

        return r.Replace(text, " ");
}
 <div class="widget-box pt-0">
     @foreach (var item in Enum.GetNames(typeof(CourseLocationType)))
     {
         <label class="pr-2 pt-1">
             @Html.RadioButtonFor(x => x.CourseLocationType, item, new { type = "radio", @class = "iCheckBox control-label" })&nbsp; @item.SplitOnCapitals()
         </label>
     }
     @Html.ValidationMessageFor(x => x.CourseLocationType)
 </div>