从Description属性中获得Enum[复制]

Possible Duplicate:
Finding an enum value by its Description Attribute

可能的副本:通过描述属性找到枚举值。

I have a generic extension method which gets the Description attribute from an Enum:

我有一个通用的扩展方法，它从枚举中获取描述属性:

enum Animal
{
    [Description("")]
    NotSet = 0,

    [Description("Giant Panda")]
    GiantPanda = 1,

    [Description("Lesser Spotted Anteater")]
    LesserSpottedAnteater = 2
}

public static string GetDescription(this Enum value)
{            
    FieldInfo field = value.GetType().GetField(value.ToString());

    DescriptionAttribute attribute
            = Attribute.GetCustomAttribute(field, typeof(DescriptionAttribute))
                as DescriptionAttribute;

    return attribute == null ? value.ToString() : attribute.Description;
}

so I can do...

所以我可以做……

string myAnimal = Animal.GiantPanda.GetDescription(); // = "Giant Panda"

now, I'm trying to work out the equivalent function in the other direction, something like...

现在，我试着算出另一个方向上的等价函数，比如。

Animal a = (Animal)Enum.GetValueFromDescription("Giant Panda", typeof(Animal));

6 个解决方案

#1

public static class EnumEx
{
    public static T GetValueFromDescription<T>(string description)
    {
        var type = typeof(T);
        if(!type.IsEnum) throw new InvalidOperationException();
        foreach(var field in type.GetFields())
        {
            var attribute = Attribute.GetCustomAttribute(field,
                typeof(DescriptionAttribute)) as DescriptionAttribute;
            if(attribute != null)
            {
                if(attribute.Description == description)
                    return (T)field.GetValue(null);
            }
            else
            {
                if(field.Name == description)
                    return (T)field.GetValue(null);
            }
        }
        throw new ArgumentException("Not found.", "description");
        // or return default(T);
    }
}

Usage:

用法:

var panda = EnumEx.GetValueFromDescription<Animal>("Giant Panda");

#2

rather than extension methods, just try a couple of static methods

只需尝试一些静态方法，而不是扩展方法。

public static class Utility
{
    public static string GetDescriptionFromEnumValue(Enum value)
    {
        DescriptionAttribute attribute = value.GetType()
            .GetField(value.ToString())
            .GetCustomAttributes(typeof (DescriptionAttribute), false)
            .SingleOrDefault() as DescriptionAttribute;
        return attribute == null ? value.ToString() : attribute.Description;
    }

    public static T GetEnumValueFromDescription<T>(string description)
    {
        var type = typeof(T);
        if (!type.IsEnum)
            throw new ArgumentException();
        FieldInfo[] fields = type.GetFields();
        var field = fields
                        .SelectMany(f => f.GetCustomAttributes(
                            typeof(DescriptionAttribute), false), (
                                f, a) => new { Field = f, Att = a })
                        .Where(a => ((DescriptionAttribute)a.Att)
                            .Description == description).SingleOrDefault();
        return field == null ? default(T) : (T)field.Field.GetRawConstantValue();
    }
}

and use here

这里使用

var result1 = Utility.GetDescriptionFromEnumValue(
    Animal.GiantPanda);
var result2 = Utility.GetEnumValueFromDescription<Animal>(
    "Lesser Spotted Anteater");

#3

The solution works good except if you have a Web Service.

除非您有一个Web服务，否则这个解决方案很有用。

You would need to do the Following as the Description Attribute is not serializable.

您需要执行以下操作，因为Description属性不是可序列化的。

[DataContract]
public enum ControlSelectionType
{
    [EnumMember(Value = "Not Applicable")]
    NotApplicable = 1,
    [EnumMember(Value = "Single Select Radio Buttons")]
    SingleSelectRadioButtons = 2,
    [EnumMember(Value = "Completely Different Display Text")]
    SingleSelectDropDownList = 3,
}

public static string GetDescriptionFromEnumValue(Enum value)
{
        EnumMemberAttribute attribute = value.GetType()
            .GetField(value.ToString())
            .GetCustomAttributes(typeof(EnumMemberAttribute), false)
            .SingleOrDefault() as EnumMemberAttribute;
        return attribute == null ? value.ToString() : attribute.Value;
}

#4

Should be pretty straightforward, its just the reverse of your previous method;

应该很简单，它与之前的方法正好相反;

public static int GetEnumFromDescription(string description, Type enumType)
{
    foreach (var field in enumType.GetFields())
    {
        DescriptionAttribute attribute
            = Attribute.GetCustomAttribute(field, typeof(DescriptionAttribute))as DescriptionAttribute;
        if(attribute == null)
            continue;
        if(attribute.Description == description)
        {
            return (int) field.GetValue(null);
        }
    }
    return 0;
}

Usage:

用法:

Console.WriteLine((Animal)GetEnumFromDescription("Giant Panda",typeof(Animal)));

#5

You can't extend Enum as it's a static class. You can only extend instances of a type. With this in mind, you're going to have to create a static method yourself to do this; the following should work when combined with your existing method GetDescription:

您不能将Enum扩展为静态类。您只能扩展类型的实例。考虑到这一点，你需要创建一个静态方法来完成这个;当与您现有的方法GetDescription相结合时，以下内容应该有效:

public static class EnumHelper
{
    public static T GetEnumFromString<T>(string value)
    {
        if (Enum.IsDefined(typeof(T), value))
        {
            return (T)Enum.Parse(typeof(T), value, true);
        }
        else
        {
            string[] enumNames = Enum.GetNames(typeof(T));
            foreach (string enumName in enumNames)
            {  
                object e = Enum.Parse(typeof(T), enumName);
                if (value == GetDescription((Enum)e))
                {
                    return (T)e;
                }
            }
        }
        throw new ArgumentException("The value '" + value 
            + "' does not match a valid enum name or description.");
    }
}

And the usage of it would be something like this:

它的用法是这样的:

Animal giantPanda = EnumHelper.GetEnumFromString<Animal>("Giant Panda");

#6

You need to iterate through all the enum values in Animal and return the value that matches the description you need.

您需要遍历动物的所有枚举值，并返回与您需要的描述相匹配的值。