C＃获取枚举值 [英] C# Getting Enum values

问题描述

我有一个包含枚举以下（例如）：

I have a enum containing the following (for example):

• UnitedKingdom的买家，
• UnitedStates的，
• 在法国，
• 葡萄牙

在我的code我使用 Country.UnitedKingdom ，但我想有值英国如果我给它一个字符串例如。

In my code I use Country.UnitedKingdom but I want to have the value be UK if I assign it to a string for example.

这可能吗？

推荐答案

您不能枚举值分配给一个字符串的开始。你得叫的ToString（），这将转换成 Country.UnitedKingdom 来来自国家UnitedStates。

You can't assign an enum value to a string to start with. You'd have to call ToString(), which would convert Country.UnitedKingdom to "UnitedKingdom".

有两种选择自己的建议：

Two options suggest themselves:

• 创建一个词典＆LT;国家，串＆GT;
• 在switch语句
• 在每一个装饰用的价值属性，并加载与反思

有关他们每个人的意见......

Comments about each of them...

样品$ C $下词典＆LT;国家，串＆GT;

Sample code for Dictionary<Country,string>

using System;
using System.Collections.Generic;

enum Country
{
    UnitedKingdom, 
    UnitedStates,
    France,
    Portugal
}

class Test
{
    static readonly Dictionary<Country, string> CountryNames =
        new Dictionary<Country, string>
    {
        { Country.UnitedKingdom, "UK" },
        { Country.UnitedStates, "US" },
    };

    static string ConvertCountry(Country country) 
    {
        string name;
        return (CountryNames.TryGetValue(country, out name))
            ? name : country.ToString();
    }

    static void Main()
    {
        Console.WriteLine(ConvertCountry(Country.UnitedKingdom));
        Console.WriteLine(ConvertCountry(Country.UnitedStates));
        Console.WriteLine(ConvertCountry(Country.France));
    }
}

您可能希望把 ConvertCountry 逻辑到一个扩展方法。例如：

You might want to put the logic of ConvertCountry into an extension method. For example:

// Put this in a non-nested static class
public static string ToBriefName(this Country country) 
{
    string name;
    return (CountryNames.TryGetValue(country, out name))
        ? name : country.ToString();
}

然后，你可以写：

Then you could write:

string x = Country.UnitedKingdom.ToBriefName();

正如在评论中，默认的字典比较器将包括拳击，这是不理想的。对于一次性的，我会住在一起，直到我发现这是一个瓶颈。如果我要多枚举这样做，我会写一个可重用的类。

As mentioned in the comments, the default dictionary comparer will involve boxing, which is non-ideal. For a one-off, I'd live with that until I found it was a bottleneck. If I were doing this for multiple enums, I'd write a reusable class.

switch语句

我同意 使用开关暗示yshuditelu的答案语句比较少的情况。然而，由于每个案件都将是一个单独的语句，我个人改变我的编码风格针对这种情况，保持code紧凑，但可读的：

I agree with yshuditelu's answer suggesting using a switch statement for relatively few cases. However, as each case is going to be a single statement, I'd personally change my coding style for this situation, to keep the code compact but readable:

public static string ToBriefName(this Country country) 
{
    switch (country)
    {
        case Country.UnitedKingdom:  return "UK";
        case Country.UnitedStates:   return "US";
        default:                     return country.ToString();
    }
}

您可以添加更多的情况下，这个没有它变得过于庞大，而且很容易从对面枚举值蒙上你的眼睛的返回值。

You can add more cases to this without it getting too huge, and it's easy to cast your eyes across from enum value to the return value.

DescriptionAttribute

DescriptionAttribute

href="http://stackoverflow.com/questions/1008090/c-enum-values​​/1008139#1008139">瑞士雷达表作出有关$ C $下<$ C $点 DescriptionAttribute 是可重复使用的是一个很好的，但在这种情况下，我建议你不要使用反射每次你需要得到一个值的时间。我可能会写一个通用的静态类保持一个查找表（可能是一个词典，可能与中提到的注释的自定义比较）。扩展方法不能在泛型类中定义，所以你可能最终的东西，如：

The point Rado made about the code for DescriptionAttribute being reusable is a good one, but in that case I'd recommend against using reflection every time you need to get a value. I'd probably write a generic static class to hold a lookup table (probably a Dictionary, possibly with a custom comparer as mentioned in the comments). Extension methods can't be defined in generic classes, so you'd probably end up with something like:

public static class EnumExtensions
{
    public static string ToDescription<T>(this T value) where T : struct
    {
        return DescriptionLookup<T>.GetDescription(value);
    }

    private static class DescriptionLookup<T> where T : struct
    {
        static readonly Dictionary<T, string> Descriptions;

        static DescriptionLookup()
        {
            // Initialize Descriptions here, and probably check
            // that T is an enum
        }

        internal static string GetDescription(T value)
        {
            string description;
            return Descriptions.TryGetValue(value, out description)
                ? description : value.ToString();
        }
    }
}

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