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>();
}

其他回答

在Aydin和Todd回答的基础上,下面是一个扩展方法,它还可以让您从资源文件中获得名称

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

public static class EnumExtensions
{
    public static string GetDisplayName(this Enum enumValue)
    {
        var enumMember= enumValue.GetType()
                        .GetMember(enumValue.ToString());

        DisplayAttribute displayAttrib = null;
        if (enumMember.Any()) {
            displayAttrib = enumMember 
                        .First()
                        .GetCustomAttribute<DisplayAttribute>();
        }

        string name = null;
        Type resource = null;

        if (displayAttrib != null)
        {
            name = displayAttrib.Name;
            resource = displayAttrib.ResourceType;
        }

        return String.IsNullOrEmpty(name) ? enumValue.ToString()
            : resource == null ?  name
            : new ResourceManager(resource).GetString(name);
    }
}

然后像这样使用它

public enum Season 
{
    [Display(ResourceType = typeof(Resource), Name = Season_Summer")]
    Summer
}

如果你使用的是MVC 5.1或更高版本,有一个更简单、更清晰的方法:只使用数据注释(来自System.ComponentModel.DataAnnotations命名空间),如下所示:

public enum Color
{
    [Display(Name = "Dark red")]
    DarkRed,
    [Display(Name = "Very dark red")]
    VeryDarkRed,
    [Display(Name = "Red or just black?")]
    ReallyDarkRed
}

在视图中,把它放到合适的html helper中:

@Html.EnumDropDownListFor(model => model.Color)

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();
    }
}

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>

基于Aydin的回答,这里有一个不需要任何类型参数的扩展方法。

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

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

注意:应该使用GetName()而不是Name属性。这确保如果使用ResourceType属性,将返回本地化的字符串。

例子

要使用它,只需在视图中引用枚举值。

@{
    UserPromotion promo = UserPromotion.SendJobOffersByMail;
}

Promotion: @promo.GetDisplayName()

输出

促销:通过邮件发送工作邀请