我想知道是否有可能获得枚举值的属性，而不是枚举本身?例如，假设我有以下枚举:
using System.ComponentModel; // for DescriptionAttribute
enum FunkyAttributesEnum
{
[Description("Name With Spaces1")]
NameWithoutSpaces1,
[Description("Name With Spaces2")]
NameWithoutSpaces2
}
我想要的是给定枚举类型，产生枚举字符串值及其描述的二元组。
价值很简单:
Array values = System.Enum.GetValues(typeof(FunkyAttributesEnum));
foreach (int value in values)
Tuple.Value = Enum.GetName(typeof(FunkyAttributesEnum), value);
但我如何获得描述属性的值，以填充Tuple.Desc?如果属性属于枚举本身，我可以想到如何做到这一点，但我不知道如何从枚举的值中获得它。
从enum中获取字典。
public static IDictionary<string, int> ToDictionary(this Type enumType)
{
return Enum.GetValues(enumType)
.Cast<object>()
.ToDictionary(v => ((Enum)v).ToEnumDescription(), k => (int)k);
}
现在把它叫做…
var dic = typeof(ActivityType).ToDictionary();
枚举描述Ext方法
public static string ToEnumDescription(this Enum en) //ext method
{
Type type = en.GetType();
MemberInfo[] memInfo = type.GetMember(en.ToString());
if (memInfo != null && memInfo.Length > 0)
{
object[] attrs = memInfo[0].GetCustomAttributes(typeof(DescriptionAttribute), false);
if (attrs != null && attrs.Length > 0)
return ((DescriptionAttribute)attrs[0]).Description;
}
return en.ToString();
}
public enum ActivityType
{
[Description("Drip Plan Email")]
DripPlanEmail = 1,
[Description("Modification")]
Modification = 2,
[Description("View")]
View = 3,
[Description("E-Alert Sent")]
EAlertSent = 4,
[Description("E-Alert View")]
EAlertView = 5
}
添加我的解决方案的Net Framework和NetCore。
我在我的Net Framework实现中使用了这个:
public static class EnumerationExtension
{
public static string Description( this Enum value )
{
// get attributes
var field = value.GetType().GetField( value.ToString() );
var attributes = field.GetCustomAttributes( typeof( DescriptionAttribute ), false );
// return description
return attributes.Any() ? ( (DescriptionAttribute)attributes.ElementAt( 0 ) ).Description : "Description Not Found";
}
}
这并不适用于NetCore，所以我修改了它，这样做:
public static class EnumerationExtension
{
public static string Description( this Enum value )
{
// get attributes
var field = value.GetType().GetField( value.ToString() );
var attributes = field.GetCustomAttributes( false );
// Description is in a hidden Attribute class called DisplayAttribute
// Not to be confused with DisplayNameAttribute
dynamic displayAttribute = null;
if (attributes.Any())
{
displayAttribute = attributes.ElementAt( 0 );
}
// return description
return displayAttribute?.Description ?? "Description Not Found";
}
}
枚举的例子:
public enum ExportTypes
{
[Display( Name = "csv", Description = "text/csv" )]
CSV = 0
}
使用任何静态添加:
var myDescription = myEnum.Description();
我在这里合并了几个答案，以创建一个更具可扩展性的解决方案。我提供这些只是为了将来对其他人有所帮助。原文在此。
using System;
using System.ComponentModel;
public static class EnumExtensions {
// This extension method is broken out so you can use a similar pattern with
// other MetaData elements in the future. This is your base method for each.
public static T GetAttribute<T>(this Enum value) where T : Attribute {
var type = value.GetType();
var memberInfo = type.GetMember(value.ToString());
var attributes = memberInfo[0].GetCustomAttributes(typeof(T), false);
return attributes.Length > 0
? (T)attributes[0]
: null;
}
// This method creates a specific call to the above method, requesting the
// Description MetaData attribute.
public static string ToName(this Enum value) {
var attribute = value.GetAttribute<DescriptionAttribute>();
return attribute == null ? value.ToString() : attribute.Description;
}
}
这个解决方案在Enum上创建一对扩展方法。第一种方法允许您使用反射来检索与您的值相关的任何属性。第二个调用检索DescriptionAttribute并返回它的Description值。
例如，考虑使用System中的DescriptionAttribute属性。ComponentModel
using System.ComponentModel;
public enum Days {
[Description("Sunday")]
Sun,
[Description("Monday")]
Mon,
[Description("Tuesday")]
Tue,
[Description("Wednesday")]
Wed,
[Description("Thursday")]
Thu,
[Description("Friday")]
Fri,
[Description("Saturday")]
Sat
}
要使用上面的扩展方法，你现在只需调用下面的方法:
Console.WriteLine(Days.Mon.ToName());
or
var day = Days.Mon;
Console.WriteLine(day.ToName());
这段代码应该为任何枚举提供了一个不错的扩展方法，使您可以检索泛型属性。我相信它与上面的lambda函数不同，因为它使用起来更简单，而且稍微-你只需要传入泛型类型。
public static class EnumHelper
{
/// <summary>
/// Gets an attribute on an enum field value
/// </summary>
/// <typeparam name="T">The type of the attribute you want to retrieve</typeparam>
/// <param name="enumVal">The enum value</param>
/// <returns>The attribute of type T that exists on the enum value</returns>
/// <example><![CDATA[string desc = myEnumVariable.GetAttributeOfType<DescriptionAttribute>().Description;]]></example>
public static T GetAttributeOfType<T>(this Enum enumVal) where T:System.Attribute
{
var type = enumVal.GetType();
var memInfo = type.GetMember(enumVal.ToString());
var attributes = memInfo[0].GetCustomAttributes(typeof(T), false);
return (attributes.Length > 0) ? (T)attributes[0] : null;
}
}
用法如下:
string desc = myEnumVariable.GetAttributeOfType<DescriptionAttribute>().Description;
下面是从Display属性获取信息的代码。它使用泛型方法检索属性。如果没有找到该属性，它将枚举值转换为字符串，将pascal/camel大小写转换为标题大小写(此处获得的代码)
public static class EnumHelper
{
// Get the Name value of the Display attribute if the
// enum has one, otherwise use the value converted to title case.
public static string GetDisplayName<TEnum>(this TEnum value)
where TEnum : struct, IConvertible
{
var attr = value.GetAttributeOfType<TEnum, DisplayAttribute>();
return attr == null ? value.ToString().ToSpacedTitleCase() : attr.Name;
}
// Get the ShortName value of the Display attribute if the
// enum has one, otherwise use the value converted to title case.
public static string GetDisplayShortName<TEnum>(this TEnum value)
where TEnum : struct, IConvertible
{
var attr = value.GetAttributeOfType<TEnum, DisplayAttribute>();
return attr == null ? value.ToString().ToSpacedTitleCase() : attr.ShortName;
}
/// <summary>
/// Gets an attribute on an enum field value
/// </summary>
/// <typeparam name="TEnum">The enum type</typeparam>
/// <typeparam name="T">The type of the attribute you want to retrieve</typeparam>
/// <param name="value">The enum value</param>
/// <returns>The attribute of type T that exists on the enum value</returns>
private static T GetAttributeOfType<TEnum, T>(this TEnum value)
where TEnum : struct, IConvertible
where T : Attribute
{
return value.GetType()
.GetMember(value.ToString())
.First()
.GetCustomAttributes(false)
.OfType<T>()
.LastOrDefault();
}
}
这是字符串转换为title case的扩展方法:
/// <summary>
/// Converts camel case or pascal case to separate words with title case
/// </summary>
/// <param name="s"></param>
/// <returns></returns>
public static string ToSpacedTitleCase(this string s)
{
//https://stackoverflow.com/a/155486/150342
CultureInfo cultureInfo = Thread.CurrentThread.CurrentCulture;
TextInfo textInfo = cultureInfo.TextInfo;
return textInfo
.ToTitleCase(Regex.Replace(s,
"([a-z](?=[A-Z0-9])|[A-Z](?=[A-Z][a-z]))", "$1 "));
}
