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

我试着把它作为一个编辑,但它被拒绝了;我不明白为什么。

如果你用一个混合了自定义属性和普通项的Enum调用它,上面的方法会抛出一个异常。

public enum CommentType
{
    All = 1,
    Rent = 2,
    Insurance = 3,
    [Display(Name="Service Charge")]
    ServiceCharge = 4
}

因此,我稍微修改了代码,以便在尝试访问自定义属性之前检查它们,如果没有找到则使用名称。

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

public static class EnumHelper<T>
{
    public static IList<T> GetValues(Enum value)
    {
        var enumValues = new List<T>();

        foreach (FieldInfo fi in value.GetType().GetFields(BindingFlags.Static | BindingFlags.Public))
        {
            enumValues.Add((T)Enum.Parse(value.GetType(), fi.Name, false));
        }
        return enumValues;
    }

    public static T Parse(string value)
    {
        return (T)Enum.Parse(typeof(T), value, true);
    }

    public static IList<string> GetNames(Enum value)
    {
        return value.GetType().GetFields(BindingFlags.Static | BindingFlags.Public).Select(fi => fi.Name).ToList();
    }

    public static IList<string> GetDisplayValues(Enum value)
    {
        return GetNames(value).Select(obj => GetDisplayValue(Parse(obj))).ToList();
    }

    private static string lookupResource(Type resourceManagerProvider, string resourceKey)
    {
        foreach (PropertyInfo staticProperty in resourceManagerProvider.GetProperties(BindingFlags.Static | BindingFlags.NonPublic | BindingFlags.Public))
        {
            if (staticProperty.PropertyType == typeof(System.Resources.ResourceManager))
            {
                System.Resources.ResourceManager resourceManager = (System.Resources.ResourceManager)staticProperty.GetValue(null, null);
                return resourceManager.GetString(resourceKey);
            }
        }

        return resourceKey; // Fallback with the key name
    }

    public static string GetDisplayValue(T value)
    {
        var fieldInfo = value.GetType().GetField(value.ToString());

        var descriptionAttributes = fieldInfo.GetCustomAttributes(
            typeof(DisplayAttribute), false) as DisplayAttribute[];

        if (descriptionAttributes.Any() && descriptionAttributes[0].ResourceType != null)
            return lookupResource(descriptionAttributes[0].ResourceType, descriptionAttributes[0].Name);

        if (descriptionAttributes == null) return string.Empty;
        return (descriptionAttributes.Length > 0) ? descriptionAttributes[0].Name : value.ToString();
    }
}

其他回答

我试着把它作为一个编辑,但它被拒绝了;我不明白为什么。

如果你用一个混合了自定义属性和普通项的Enum调用它,上面的方法会抛出一个异常。

public enum CommentType
{
    All = 1,
    Rent = 2,
    Insurance = 3,
    [Display(Name="Service Charge")]
    ServiceCharge = 4
}

因此,我稍微修改了代码,以便在尝试访问自定义属性之前检查它们,如果没有找到则使用名称。

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

public static class EnumHelper<T>
{
    public static IList<T> GetValues(Enum value)
    {
        var enumValues = new List<T>();

        foreach (FieldInfo fi in value.GetType().GetFields(BindingFlags.Static | BindingFlags.Public))
        {
            enumValues.Add((T)Enum.Parse(value.GetType(), fi.Name, false));
        }
        return enumValues;
    }

    public static T Parse(string value)
    {
        return (T)Enum.Parse(typeof(T), value, true);
    }

    public static IList<string> GetNames(Enum value)
    {
        return value.GetType().GetFields(BindingFlags.Static | BindingFlags.Public).Select(fi => fi.Name).ToList();
    }

    public static IList<string> GetDisplayValues(Enum value)
    {
        return GetNames(value).Select(obj => GetDisplayValue(Parse(obj))).ToList();
    }

    private static string lookupResource(Type resourceManagerProvider, string resourceKey)
    {
        foreach (PropertyInfo staticProperty in resourceManagerProvider.GetProperties(BindingFlags.Static | BindingFlags.NonPublic | BindingFlags.Public))
        {
            if (staticProperty.PropertyType == typeof(System.Resources.ResourceManager))
            {
                System.Resources.ResourceManager resourceManager = (System.Resources.ResourceManager)staticProperty.GetValue(null, null);
                return resourceManager.GetString(resourceKey);
            }
        }

        return resourceKey; // Fallback with the key name
    }

    public static string GetDisplayValue(T value)
    {
        var fieldInfo = value.GetType().GetField(value.ToString());

        var descriptionAttributes = fieldInfo.GetCustomAttributes(
            typeof(DisplayAttribute), false) as DisplayAttribute[];

        if (descriptionAttributes.Any() && descriptionAttributes[0].ResourceType != null)
            return lookupResource(descriptionAttributes[0].ResourceType, descriptionAttributes[0].Name);

        if (descriptionAttributes == null) return string.Empty;
        return (descriptionAttributes.Length > 0) ? descriptionAttributes[0].Name : value.ToString();
    }
}

我想贡献与区域性相关的GetDisplayName enum扩展。希望这对以前像我一样在谷歌上搜索这个答案的人有用:

Aydin Adn和Todd提到的“标准”方式:

    public static string GetDisplayName(this Enum enumValue)
    {
        return enumValue
            .GetType()
            .GetMember(enumValue.ToString())
            .First()
            .GetCustomAttribute<DisplayAttribute>()
            .GetName();
    }

“文化相关的”方式:

    public static string GetDisplayName(this Enum enumValue, CultureInfo ci)
    {
        var displayAttr = enumValue
            .GetType()
            .GetMember(enumValue.ToString())
            .First()
            .GetCustomAttribute<DisplayAttribute>();

        var resMan = displayAttr.ResourceType?.GetProperty(@"ResourceManager", BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic).GetValue(null, null) as ResourceManager;

        return resMan?.GetString(displayAttr.Name, ci) ?? displayAttr.GetName();
    }

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

2020更新:本线程中许多函数提供的更新版本,但现在适用于c# 7.3以上:

现在你可以将泛型方法限制为枚举类型,这样你就可以编写一个方法扩展来使用所有的枚举,如下所示:

泛型扩展方法:

public static string ATexto<T>(this T enumeración) where T : struct, Enum {
    var tipo = enumeración.GetType();
    return tipo.GetMember(enumeración.ToString())
    .Where(x => x.MemberType == MemberTypes.Field && ((FieldInfo)x).FieldType == tipo).First()
    .GetCustomAttribute<DisplayAttribute>()?.Name ?? enumeración.ToString();
} 

枚举:

public enum TipoImpuesto { 
IVA, INC, [Display(Name = "IVA e INC")]IVAeINC, [Display(Name = "No aplica")]NoAplica };

如何使用:

var tipoImpuesto = TipoImpuesto.IVAeINC;
var textoTipoImpuesto = tipoImpuesto.ATexto(); // Prints "IVA e INC".

附加的,带有标志的枚举:如果你处理的是普通的枚举,上面的函数就足够了,但如果你的任何枚举都可以通过使用标志来获得多个值,那么你就需要像这样修改它(这段代码使用c# 8的特性):

    public static string ATexto<T>(this T enumeración) where T : struct, Enum {

        var tipo = enumeración.GetType();
        var textoDirecto = enumeración.ToString();

        string obtenerTexto(string textoDirecto) => tipo.GetMember(textoDirecto)
            .Where(x => x.MemberType == MemberTypes.Field && ((FieldInfo)x).FieldType == tipo)
            .First().GetCustomAttribute<DisplayAttribute>()?.Name ?? textoDirecto;

        if (textoDirecto.Contains(", ")) {

            var texto = new StringBuilder();
            foreach (var textoDirectoAux in textoDirecto.Split(", ")) {
                texto.Append($"{obtenerTexto(textoDirectoAux)}, ");
            }
            return texto.ToString()[0..^2];

        } else {
            return obtenerTexto(textoDirecto);
        }

    } 

带标志的枚举:

[Flags] public enum TipoContribuyente {
    [Display(Name = "Común")] Común = 1, 
    [Display(Name = "Gran Contribuyente")] GranContribuyente = 2, 
    Autorretenedor = 4, 
    [Display(Name = "Retenedor de IVA")] RetenedorIVA = 8, 
    [Display(Name = "Régimen Simple")] RégimenSimple = 16 } 

如何使用:

var tipoContribuyente = TipoContribuyente.RetenedorIVA | TipoContribuyente.GranContribuyente;
var textoAux = tipoContribuyente.ATexto(); // Prints "Gran Contribuyente, Retenedor de IVA".

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。