我的枚举能有友好的名称吗?[复制品]

枚举值名称必须遵循与C中所有标识符相同的命名规则,因此只有名字是正确的。

你可以用 Description 属性,正如尤里建议的。以下扩展方法使获取枚举的给定值的描述变得容易:

public static string GetDescription(this Enum value)
{
    Type type = value.GetType();
    string name = Enum.GetName(type, value);
    if (name != null)
    {
        FieldInfo field = type.GetField(name);
        if (field != null)
        {
            DescriptionAttribute attr = 
                   Attribute.GetCustomAttribute(field, 
                     typeof(DescriptionAttribute)) as DescriptionAttribute;
            if (attr != null)
            {
                return attr.Description;
            }
        }
    }
    return null;
}

您可以这样使用它:

public enum MyEnum
{
    [Description("Description for Foo")]
    Foo,
    [Description("Description for Bar")]
    Bar
}

MyEnum x = MyEnum.Foo;
string description = x.GetDescription();

如果具有以下枚举:

public enum MyEnum {
    First,
    Second,
    Third
}

您可以为声明扩展方法 MyEnum (和其他类型一样)。我刚把这个搅了起来:

namespace Extension {
    public static class ExtensionMethods {
        public static string EnumValue(this MyEnum e) {
            switch (e) {
                case MyEnum.First:
                    return "First Friendly Value";
                case MyEnum.Second:
                    return "Second Friendly Value";
                case MyEnum.Third:
                    return "Third Friendly Value";
            }
            return "Horrible Failure!!";
        }
    }
}

使用此扩展方法,以下内容现在是合法的:

Console.WriteLine(MyEnum.First.EnumValue());

希望这有帮助!!

不,但是你可以用 DescriptionAttribute 完成你想要的。

你可以使用 Description 属性获取友好名称。您可以使用以下代码:

public static string ToStringEnums(Enum en)
{
    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();
}

当枚举值为 EncryptionProviderType 你想要 enumVar.Tostring() 返回“加密提供程序类型”。

前提条件:所有枚举成员都应使用该属性应用 [Description("String to be returned by Tostring()")] .

实例枚举:

enum ExampleEnum
{
    [Description("One is one")]
    ValueOne = 1,
    [Description("Two is two")]
    ValueTow = 2
}

在你的课堂上,你可以这样使用它:

ExampleEnum enumVar = ExampleEnum.ValueOne;
Console.WriteLine(ToStringEnums(enumVar));

这个技巧的一个问题是描述属性不能本地化。我很喜欢SachaBarber的一种技术,他创建了自己版本的描述属性,该属性将从相应的资源管理器中获取值。

http://www.codeproject.com/KB/WPF/FriendlyEnums.aspx

尽管本文讨论了WPF开发人员在绑定到枚举时通常会遇到的问题,但是您可以直接跳到他创建本地化描述属性的部分。

一些伟大的解决方案已经发布。当我遇到这个问题时,我想双向进行:将枚举转换为描述,并将与描述匹配的字符串转换为枚举。

我有两种变体,慢的和快的。两者都从枚举转换为字符串,从字符串转换为枚举。我的问题是我有这样的枚举,有些元素需要属性,有些不需要。我不想在不需要属性的元素上放置属性。我目前有大约一百个这样的总数:

public enum POS
{   
    CC, //  Coordinating conjunction
    CD, //  Cardinal Number
    DT, //  Determiner
    EX, //  Existential there
    FW, //  Foreign Word
    IN, //  Preposision or subordinating conjunction
    JJ, //  Adjective
    [System.ComponentModel.Description("WP$")]
    WPDollar, //$   Possessive wh-pronoun
    WRB, //     Wh-adverb
    [System.ComponentModel.Description("#")]
    Hash,
    [System.ComponentModel.Description("$")]
    Dollar,
    [System.ComponentModel.Description("''")]
    DoubleTick,
    [System.ComponentModel.Description("(")]
    LeftParenth,
    [System.ComponentModel.Description(")")]
    RightParenth,
    [System.ComponentModel.Description(",")]
    Comma,
    [System.ComponentModel.Description(".")]
    Period,
    [System.ComponentModel.Description(":")]
    Colon,
    [System.ComponentModel.Description("``")]
    DoubleBackTick,
    };

处理这个问题的第一个方法是缓慢的,基于我在这里和网络周围看到的建议。它很慢,因为我们对每一个转换都进行反射:

using System;
using System.Collections.Generic;
namespace CustomExtensions
{

/// <summary>
/// uses extension methods to convert enums with hypens in their names to underscore and other variants
public static class EnumExtensions
{
    /// <summary>
    /// Gets the description string, if available. Otherwise returns the name of the enum field
    /// LthWrapper.POS.Dollar.GetString() yields "$", an impossible control character for enums
    /// </summary>
    /// <param name="value"></param>
    /// <returns></returns>
    public static string GetStringSlow(this Enum value)
    {
        Type type = value.GetType();
        string name = Enum.GetName(type, value);
        if (name != null)
        {
            System.Reflection.FieldInfo field = type.GetField(name);
            if (field != null)
            {
                System.ComponentModel.DescriptionAttribute attr =
                       Attribute.GetCustomAttribute(field,
                         typeof(System.ComponentModel.DescriptionAttribute)) as System.ComponentModel.DescriptionAttribute;
                if (attr != null)
                {
                    //return the description if we have it
                    name = attr.Description; 
                }
            }
        }
        return name;
    }

    /// <summary>
    /// Converts a string to an enum field using the string first; if that fails, tries to find a description
    /// attribute that matches. 
    /// "$".ToEnum<LthWrapper.POS>() yields POS.Dollar
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="value"></param>
    /// <returns></returns>
    public static T ToEnumSlow<T>(this string value) //, T defaultValue)
    {
        T theEnum = default(T);

        Type enumType = typeof(T);

        //check and see if the value is a non attribute value
        try
        {
            theEnum = (T)Enum.Parse(enumType, value);
        }
        catch (System.ArgumentException e)
        {
            bool found = false;
            foreach (T enumValue in Enum.GetValues(enumType))
            {
                System.Reflection.FieldInfo field = enumType.GetField(enumValue.ToString());

                System.ComponentModel.DescriptionAttribute attr =
                           Attribute.GetCustomAttribute(field,
                             typeof(System.ComponentModel.DescriptionAttribute)) as System.ComponentModel.DescriptionAttribute;

                if (attr != null && attr.Description.Equals(value))
                {
                    theEnum = enumValue;
                    found = true;
                    break;

                }
            }
            if( !found )
                throw new ArgumentException("Cannot convert " + value + " to " + enumType.ToString());
        }

        return theEnum;
    }
}
}

问题是你每次都在反思。我还没有衡量这样做对性能的影响,但这似乎令人担忧。更糟糕的是,我们反复计算这些昂贵的转换,而不缓存它们。

相反,我们可以使用一个静态构造函数来用这个转换信息填充一些字典,然后在需要时查找这个信息。显然静态类(扩展方法所需)可以有构造函数和字段:)

using System;
using System.Collections.Generic;
namespace CustomExtensions
{

/// <summary>
/// uses extension methods to convert enums with hypens in their names to underscore and other variants
/// I'm not sure this is a good idea. While it makes that section of the code much much nicer to maintain, it 
/// also incurs a performance hit via reflection. To circumvent this, I've added a dictionary so all the lookup can be done once at 
/// load time. It requires that all enums involved in this extension are in this assembly.
/// </summary>
public static class EnumExtensions
{
    //To avoid collisions, every Enum type has its own hash table
    private static readonly Dictionary<Type, Dictionary<object,string>> enumToStringDictionary = new Dictionary<Type,Dictionary<object,string>>();
    private static readonly Dictionary<Type, Dictionary<string, object>> stringToEnumDictionary = new Dictionary<Type, Dictionary<string, object>>();

    static EnumExtensions()
    {
        //let's collect the enums we care about
        List<Type> enumTypeList = new List<Type>();

        //probe this assembly for all enums
        System.Reflection.Assembly assembly = System.Reflection.Assembly.GetExecutingAssembly();
        Type[] exportedTypes = assembly.GetExportedTypes();

        foreach (Type type in exportedTypes)
        {
            if (type.IsEnum)
                enumTypeList.Add(type);
        }

        //for each enum in our list, populate the appropriate dictionaries
        foreach (Type type in enumTypeList)
        {
            //add dictionaries for this type
            EnumExtensions.enumToStringDictionary.Add(type, new Dictionary<object,string>() );
            EnumExtensions.stringToEnumDictionary.Add(type, new Dictionary<string,object>() );

            Array values = Enum.GetValues(type);

            //its ok to manipulate 'value' as object, since when we convert we're given the type to cast to
            foreach (object value in values)
            {
                System.Reflection.FieldInfo fieldInfo = type.GetField(value.ToString());

                //check for an attribute 
                System.ComponentModel.DescriptionAttribute attribute =
                       Attribute.GetCustomAttribute(fieldInfo,
                         typeof(System.ComponentModel.DescriptionAttribute)) as System.ComponentModel.DescriptionAttribute;

                //populate our dictionaries
                if (attribute != null)
                {
                    EnumExtensions.enumToStringDictionary[type].Add(value, attribute.Description);
                    EnumExtensions.stringToEnumDictionary[type].Add(attribute.Description, value);
                }
                else
                {
                    EnumExtensions.enumToStringDictionary[type].Add(value, value.ToString());
                    EnumExtensions.stringToEnumDictionary[type].Add(value.ToString(), value);
                }
            }
        }
    }

    public static string GetString(this Enum value)
    {
        Type type = value.GetType();
        string aString = EnumExtensions.enumToStringDictionary[type][value];
        return aString; 
    }

    public static T ToEnum<T>(this string value)
    {
        Type type = typeof(T);
        T theEnum = (T)EnumExtensions.stringToEnumDictionary[type][value];
        return theEnum;
    }
 }
}

看看转换方法现在有多紧。我能想到的唯一缺陷是,这要求所有转换后的枚举都在当前程序集中。另外,我只关心导出的枚举,但是如果您愿意,您可以更改它。

这是如何调用方法

 string x = LthWrapper.POS.Dollar.GetString();
 LthWrapper.POS y = "PRP$".ToEnum<LthWrapper.POS>();

public enum myEnum
{
         ThisNameWorks, 
         This_Name_can_be_used_instead,

}

在阅读了许多关于这个主题的资源(包括stackoverflow)之后,我发现并不是所有的解决方案都能正常工作。下面是我们试图解决的问题。

基本上,如果枚举存在,我们从DescriptionAttribute中获取它的友好名称。
如果没有,我们使用regex来确定枚举名称中的单词并添加空格。

下一个版本,我们将使用另一个属性来标记是否可以/应该从可本地化的资源文件中获取友好名称。

下面是测试用例。如果您还有其他未通过的测试用例,请报告。

public static class EnumHelper
{
    public static string ToDescription(Enum value)
    {
        if (value == null)
        {
            return string.Empty;
        }

        if (!Enum.IsDefined(value.GetType(), value))
        {
            return string.Empty;
        }

        FieldInfo fieldInfo = value.GetType().GetField(value.ToString());
        if (fieldInfo != null)
        {
            DescriptionAttribute[] attributes =
                fieldInfo.GetCustomAttributes(typeof (DescriptionAttribute), false) as DescriptionAttribute[];
            if (attributes != null && attributes.Length > 0)
            {
                return attributes[0].Description;
            }
        }

        return StringHelper.ToFriendlyName(value.ToString());
    }
}

public static class StringHelper
{
    public static bool IsNullOrWhiteSpace(string value)
    {
        return value == null || string.IsNullOrEmpty(value.Trim());
    }

    public static string ToFriendlyName(string value)
    {
        if (value == null) return string.Empty;
        if (value.Trim().Length == 0) return string.Empty;

        string result = value;

        result = string.Concat(result.Substring(0, 1).ToUpperInvariant(), result.Substring(1, result.Length - 1));

        const string pattern = @"([A-Z]+(?![a-z])|\d+|[A-Z][a-z]+|(?![A-Z])[a-z]+)+";

        List<string> words = new List<string>();
        Match match = Regex.Match(result, pattern);
        if (match.Success)
        {
            Group group = match.Groups[1];
            foreach (Capture capture in group.Captures)
            {
                words.Add(capture.Value);
            }
        }

        return string.Join(" ", words.ToArray());
    }
}


    [TestMethod]
    public void TestFriendlyName()
    {
        string[][] cases =
            {
                new string[] {null, string.Empty},
                new string[] {string.Empty, string.Empty},
                new string[] {" ", string.Empty}, 
                new string[] {"A", "A"},
                new string[] {"z", "Z"},

                new string[] {"Pascal", "Pascal"},
                new string[] {"camel", "Camel"},

                new string[] {"PascalCase", "Pascal Case"}, 
                new string[] {"ABCPascal", "ABC Pascal"}, 
                new string[] {"PascalABC", "Pascal ABC"}, 
                new string[] {"Pascal123", "Pascal 123"}, 
                new string[] {"Pascal123ABC", "Pascal 123 ABC"}, 
                new string[] {"PascalABC123", "Pascal ABC 123"}, 
                new string[] {"123Pascal", "123 Pascal"}, 
                new string[] {"123ABCPascal", "123 ABC Pascal"}, 
                new string[] {"ABC123Pascal", "ABC 123 Pascal"}, 

                new string[] {"camelCase", "Camel Case"}, 
                new string[] {"camelABC", "Camel ABC"}, 
                new string[] {"camel123", "Camel 123"}, 
            };

        foreach (string[] givens in cases)
        {
            string input = givens[0];
            string expected = givens[1];
            string output = StringHelper.ToFriendlyName(input);

            Assert.AreEqual(expected, output);
        }
    }
}

它们遵循与变量名相同的命名规则。 因此,它们不应该包含空格。

另外,你的建议无论如何都是非常糟糕的做法。

枚举名与普通变量名的规则相同,即名称中间没有空格或圆点…不过我还是认为第一个相当友好的…

这是一个糟糕的主意,但确实有效。

    public enum myEnum
{
    ThisNameWorks,
    ThisNameDoesntWork149141331,// This Name doesn't work
    NeitherDoesThis1849204824// Neither.does.this;
}

class Program
{
    private static unsafe void ChangeString(string original, string replacement)
    {
        if (original.Length < replacement.Length)
            throw new ArgumentException();

        fixed (char* pDst = original)
        fixed (char* pSrc = replacement)
        {
            // Update the length of the original string
            int* lenPtr = (int*)pDst;
            lenPtr[-1] = replacement.Length;

            // Copy the characters
            for (int i = 0; i < replacement.Length; i++)
                pDst[i] = pSrc[i];
        }
    }

    public static unsafe void Initialize()
    {
        ChangeString(myEnum.ThisNameDoesntWork149141331.ToString(), "This Name doesn't work");
        ChangeString(myEnum.NeitherDoesThis1849204824.ToString(), "Neither.does.this");
    }

    static void Main(string[] args)
    {
        Console.WriteLine(myEnum.ThisNameWorks);
        Console.WriteLine(myEnum.ThisNameDoesntWork149141331);
        Console.WriteLine(myEnum.NeitherDoesThis1849204824);

        Initialize();

        Console.WriteLine(myEnum.ThisNameWorks);
        Console.WriteLine(myEnum.ThisNameDoesntWork149141331);
        Console.WriteLine(myEnum.NeitherDoesThis1849204824);
    }

要求

1. 枚举名称的字符数必须等于或大于所需的字符串数。

2. 你的枚举名不应该在任何地方重复,只是为了防止字符串插入把事情搞砸。

为什么这是个坏主意(几个原因)

1. 您的枚举名称由于需求而变得丑陋

2. 它需要您尽早调用初始化方法。

3. 不安全指针

4. 如果字符串的内部格式发生更改,例如,如果长度字段被移动,则说明

5. 如果Enum.ToString()曾经更改过,使它只返回一个副本,那么您就完蛋了

6. Raymond Chen会抱怨您使用了未记录的功能,以及CLR团队无法在下一周的.NET工作中优化将运行时间缩短50%是您的错。

我认为您希望向用户显示枚举值,因此,您希望它们具有一些友好的名称。

我的建议是:

使用枚举类型模式。虽然它需要一些努力来实现,但它确实是值得的。

public class MyEnum
{  
    public static readonly MyEnum Enum1=new MyEnum("This will work",1);
    public static readonly MyEnum Enum2=new MyEnum("This.will.work.either",2);
    public static readonly MyEnum[] All=new []{Enum1,Enum2};
    private MyEnum(string name,int value)
    {
        Name=name;
        Value=value;
    }

    public string Name{get;set;}
    public int Value{get;set;}

    public override string ToString()
    {
        return Name;    
    }
}