How to get the Display Name Attribute of an Enum m

问题:

I\'ve got a property in my model called \"Promotion\" that its type is a flag enum called \"UserPromotion\". Members of my enum have display attributes set as follows:

[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
}

Now I want to be able to create say a ul in my view to show the selected values of my \"Promotion\" property. This is what I have done so far but the problem is that how can I get the display names here?

<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>

回答1:

UPDATE

First solution was focused on getting display names from enum. Code below should be exact solution for your problem.

You can use this helper class for enums:

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[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();
    }
}

And then you can use it in your view as following:

<ul>
    @foreach (var value in @EnumHelper<UserPromotion>.GetValues(UserPromotion.None))
    {
         if (value == Model.JobSeeker.Promotion)
        {
            var description = EnumHelper<UserPromotion>.GetDisplayValue(value);
            <li>@Html.DisplayFor(e => description )</li>
        }
    }
</ul>

Hope it helps! :)

回答2:

One liner - Fluent syntax

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>();
    }
}

---

Example

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);
    } 
}

---

Output

Which season is it?
It\'s summer

回答3:

Building on Aydin\'s great answer, here\'s an extension method that doesn\'t require any type parameters.

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();
    }
}

NOTE: GetName() should be used instead of the Name property. This ensures that the localized string will be returned if using the ResourceType attribute property.

Example

To use it, just reference the enum value in your view.

@{
    UserPromotion promo = UserPromotion.SendJobOffersByMail;
}

Promotion: @promo.GetDisplayName()

Output

Promotion: Send Job Offers By Mail

回答4:

Based on Aydin\'s answer I would suggest a less \"duplicatious\" implementation (because we could easily get the Type from the Enum value itself, instead of providing it as a parameter