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。
public enum DataFilters
{
[Display(Name= "Equals")]
Equals = 1,// Display Name and Enum Name are same
[Display(Name= "Does Not Equal")]
DoesNotEqual = 2, // Display Name and Enum Name are different
}
在这个例子中它会产生错误1 "等于"
public static string GetDisplayName(this Enum enumValue)
{
var enumMember = enumValue.GetType().GetMember(enumValue.ToString()).First();
return enumMember.GetCustomAttribute<DisplayAttribute>() != null ? enumMember.GetCustomAttribute<DisplayAttribute>().Name : enumMember.Name;
}
如果它是相同的返回enum名称而不是显示名称因为
enumMember.GetCustomAttribute ()
如果displayname和enum name相同，则返回null .....
我这回答设置一个组合框从枚举属性，这是伟大的。
然后，我需要编写反向代码，以便从框中获得选择并返回正确类型的enum。
我还修改了代码，以处理缺少属性的情况
为了下一个人的利益，这是我的最终解决方案
public static class Program
{
static void Main(string[] args)
{
// display the description attribute from the enum
foreach (Colour type in (Colour[])Enum.GetValues(typeof(Colour)))
{
Console.WriteLine(EnumExtensions.ToName(type));
}
// Get the array from the description
string xStr = "Yellow";
Colour thisColour = EnumExtensions.FromName<Colour>(xStr);
Console.ReadLine();
}
public enum Colour
{
[Description("Colour Red")]
Red = 0,
[Description("Colour Green")]
Green = 1,
[Description("Colour Blue")]
Blue = 2,
Yellow = 3
}
}
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);
// check if no attributes have been specified.
if (((Array)attributes).Length > 0)
{
return (T)attributes[0];
}
else
{
return 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;
}
/// <summary>
/// Find the enum from the description attribute.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="desc"></param>
/// <returns></returns>
public static T FromName<T>(this string desc) where T : struct
{
string attr;
Boolean found = false;
T result = (T)Enum.GetValues(typeof(T)).GetValue(0);
foreach (object enumVal in Enum.GetValues(typeof(T)))
{
attr = ((Enum)enumVal).ToName();
if (attr == desc)
{
result = (T)enumVal;
found = true;
break;
}
}
if (!found)
{
throw new Exception();
}
return result;
}
}
}
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;
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();
