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>
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();
}
}
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)
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
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