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2023-04-24 09:00:02

Enum的字符串表示形式

我有以下列举:

public enum AuthenticationMethod
{
    FORMS = 1,
    WINDOWSAUTHENTICATION = 2,
    SINGLESIGNON = 3
}

然而问题是，当我请求AuthenticationMethod时，我需要“FORMS”这个词。表单而不是id

对于这个问题，我找到了以下解决方案(链接):

首先，我需要创建一个自定义属性“StringValue”:

public class StringValue : System.Attribute
{
    private readonly string _value;

    public StringValue(string value)
    {
        _value = value;
    }

    public string Value
    {
        get { return _value; }
    }

}

然后我可以将这个属性添加到我的枚举器中:

public enum AuthenticationMethod
{
    [StringValue("FORMS")]
    FORMS = 1,
    [StringValue("WINDOWS")]
    WINDOWSAUTHENTICATION = 2,
    [StringValue("SSO")]
    SINGLESIGNON = 3
}

当然，我需要一些东西来检索StringValue:

public static class StringEnum
{
    public static string GetStringValue(Enum value)
    {
        string output = null;
        Type type = value.GetType();

        //Check first in our cached results...

        //Look for our 'StringValueAttribute' 

        //in the field's custom attributes

        FieldInfo fi = type.GetField(value.ToString());
        StringValue[] attrs =
           fi.GetCustomAttributes(typeof(StringValue),
                                   false) as StringValue[];
        if (attrs.Length > 0)
        {
            output = attrs[0].Value;
        }

        return output;
    }
}

很好，现在我已经有了工具来获取枚举器的字符串值。 然后我可以这样使用它:

string valueOfAuthenticationMethod = StringEnum.GetStringValue(AuthenticationMethod.FORMS);

好的，现在所有这些工作就像一个魅力，但我发现它有很多工作。我想知道有没有更好的解决办法。

我还尝试了一些字典和静态属性，但这也不是更好。

当前回答

我的变体

public struct Colors
{
    private String current;

    private static string red = "#ff0000";
    private static string green = "#00ff00";
    private static string blue = "#0000ff";

    private static IList<String> possibleColors; 

    public static Colors Red { get { return (Colors) red; } }
    public static Colors Green { get { return (Colors) green; } }
    public static Colors Blue { get { return (Colors) blue; } }

    static Colors()
    {
        possibleColors = new List<string>() {red, green, blue};
    }

    public static explicit operator String(Colors value)
    {
        return value.current;
    }

    public static explicit operator Colors(String value)
    {
        if (!possibleColors.Contains(value))
        {
            throw new InvalidCastException();
        }

        Colors color = new Colors();
        color.current = value;
        return color;
    }

    public static bool operator ==(Colors left, Colors right)
    {
        return left.current == right.current;
    }

    public static bool operator !=(Colors left, Colors right)
    {
        return left.current != right.current;
    }

    public bool Equals(Colors other)
    {
        return Equals(other.current, current);
    }

    public override bool Equals(object obj)
    {
        if (ReferenceEquals(null, obj)) return false;
        if (obj.GetType() != typeof(Colors)) return false;
        return Equals((Colors)obj);
    }

    public override int GetHashCode()
    {
        return (current != null ? current.GetHashCode() : 0);
    }

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

代码看起来有点丑，但是这个结构体的用法很有代表性。

Colors color1 = Colors.Red;
Console.WriteLine(color1); // #ff0000

Colors color2 = (Colors) "#00ff00";
Console.WriteLine(color2); // #00ff00

// Colors color3 = "#0000ff"; // Compilation error
// String color4 = Colors.Red; // Compilation error

Colors color5 = (Colors)"#ff0000";
Console.WriteLine(color1 == color5); // True

Colors color6 = (Colors)"#00ff00";
Console.WriteLine(color1 == color6); // False

此外，我认为，如果需要大量这样的枚举，可能会使用代码生成(例如T4)。

2012-02-01 16:00:37

其他回答

试试type-safe-enum模式。

public sealed class AuthenticationMethod {

    private readonly String name;
    private readonly int value;

    public static readonly AuthenticationMethod FORMS = new AuthenticationMethod (1, "FORMS");
    public static readonly AuthenticationMethod WINDOWSAUTHENTICATION = new AuthenticationMethod (2, "WINDOWS");
    public static readonly AuthenticationMethod SINGLESIGNON = new AuthenticationMethod (3, "SSN");        

    private AuthenticationMethod(int value, String name){
        this.name = name;
        this.value = value;
    }

    public override String ToString(){
        return name;
    }

}

更新 显式(或隐式)类型转换可以通过

adding static field with mapping private static readonly Dictionary<string, AuthenticationMethod> instance = new Dictionary<string,AuthenticationMethod>(); n.b. In order that the initialisation of the the "enum member" fields doesn't throw a NullReferenceException when calling the instance constructor, be sure to put the Dictionary field before the "enum member" fields in your class. This is because static field initialisers are called in declaration order, and before the static constructor, creating the weird and necessary but confusing situation that the instance constructor can be called before all static fields have been initialised, and before the static constructor is called. filling this mapping in instance constructor instance[name] = this; and adding user-defined type conversion operator public static explicit operator AuthenticationMethod(string str) { AuthenticationMethod result; if (instance.TryGetValue(str, out result)) return result; else throw new InvalidCastException(); }

2009-01-08 14:29:12

更新:访问这个页面，8年后，在很长一段时间没有接触c#之后，看起来我的答案不再是最好的解决方案。我非常喜欢与属性-函数绑定的转换器解决方案。

如果你正在阅读这篇文章，请确保你也查看了其他答案。(提示:它们在这个上面)

和你们大多数人一样，我非常喜欢Jakub Šturc所选的答案，但我也非常讨厌复制粘贴代码，并尽可能少地这样做。

因此，我决定使用一个EnumBase类，从其中继承/内置大部分功能，从而使我能够专注于内容而不是行为。

这种方法的主要问题是基于这样一个事实，即尽管Enum值是类型安全的实例，但交互是与Enum Class类型的静态实现进行的。 所以在泛型魔法的帮助下，我想我终于得到了正确的组合。 希望有人能像我一样觉得这个有用。

我将从Jakub的例子开始，但是使用继承和泛型:

public sealed class AuthenticationMethod : EnumBase<AuthenticationMethod, int>
{
    public static readonly AuthenticationMethod FORMS =
        new AuthenticationMethod(1, "FORMS");
    public static readonly AuthenticationMethod WINDOWSAUTHENTICATION =
        new AuthenticationMethod(2, "WINDOWS");
    public static readonly AuthenticationMethod SINGLESIGNON =
        new AuthenticationMethod(3, "SSN");

    private AuthenticationMethod(int Value, String Name)
        : base( Value, Name ) { }
    public new static IEnumerable<AuthenticationMethod> All
    { get { return EnumBase<AuthenticationMethod, int>.All; } }
    public static explicit operator AuthenticationMethod(string str)
    { return Parse(str); }
}

这里是基类:

using System;
using System.Collections.Generic;
using System.Linq; // for the .AsEnumerable() method call

// E is the derived type-safe-enum class
// - this allows all static members to be truly unique to the specific
//   derived class
public class EnumBase<E, T> where E: EnumBase<E, T>
{
    #region Instance code
    public T Value { get; private set; }
    public string Name { get; private set; }

    protected EnumBase(T EnumValue, string Name)
    {
        Value = EnumValue;
        this.Name = Name;
        mapping.Add(Name, this);
    }

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

    #region Static tools
    static private readonly Dictionary<string, EnumBase<E, T>> mapping;
    static EnumBase() { mapping = new Dictionary<string, EnumBase<E, T>>(); }
    protected static E Parse(string name)
    {
        EnumBase<E, T> result;
        if (mapping.TryGetValue(name, out result))
        {
            return (E)result;
        }

        throw new InvalidCastException();
    }
    // This is protected to force the child class to expose it's own static
    // method.
    // By recreating this static method at the derived class, static
    // initialization will be explicit, promising the mapping dictionary
    // will never be empty when this method is called.
    protected static IEnumerable<E> All
    { get { return mapping.Values.AsEnumerable().Cast<E>(); } }
    #endregion
}
2011-12-02 07:43:50

如果我理解正确，你可以简单地使用.ToString()从值中检索enum的名称(假设它已经被转换为enum); 如果你有裸整型(比如从数据库或其他地方)，你可以先将它强制转换为枚举。 下面的两个方法都将获得枚举名称。

AuthenticationMethod myCurrentSetting = AuthenticationMethod.FORMS;
Console.WriteLine(myCurrentSetting); // Prints: FORMS
string name = Enum.GetNames(typeof(AuthenticationMethod))[(int)myCurrentSetting-1];
Console.WriteLine(name); // Prints: FORMS

但是请记住，第二种技术假设您使用的是int型，并且您的索引基于1(而不是基于0)。相比之下，GetNames函数也相当繁重，每次调用它都要生成一个完整的数组。 正如您在第一种技术中看到的，. tostring()实际上是隐式调用的。 这两个问题都已经在答案中提到了，当然，我只是想澄清它们之间的区别。

2015-09-28 09:33:15

对我来说，实用的方法是类中类，sample:

public class MSEModel
{
    class WITS
    {
        public const string DATE = "5005";
        public const string TIME = "5006";
        public const string MD = "5008";
        public const string ROP = "5075";
        public const string WOB = "5073";
        public const string RPM = "7001";
... 
    }
2013-02-06 13:46:33

我的变体

public struct Colors
{
    private String current;

    private static string red = "#ff0000";
    private static string green = "#00ff00";
    private static string blue = "#0000ff";

    private static IList<String> possibleColors; 

    public static Colors Red { get { return (Colors) red; } }
    public static Colors Green { get { return (Colors) green; } }
    public static Colors Blue { get { return (Colors) blue; } }

    static Colors()
    {
        possibleColors = new List<string>() {red, green, blue};
    }

    public static explicit operator String(Colors value)
    {
        return value.current;
    }

    public static explicit operator Colors(String value)
    {
        if (!possibleColors.Contains(value))
        {
            throw new InvalidCastException();
        }

        Colors color = new Colors();
        color.current = value;
        return color;
    }

    public static bool operator ==(Colors left, Colors right)
    {
        return left.current == right.current;
    }

    public static bool operator !=(Colors left, Colors right)
    {
        return left.current != right.current;
    }

    public bool Equals(Colors other)
    {
        return Equals(other.current, current);
    }

    public override bool Equals(object obj)
    {
        if (ReferenceEquals(null, obj)) return false;
        if (obj.GetType() != typeof(Colors)) return false;
        return Equals((Colors)obj);
    }

    public override int GetHashCode()
    {
        return (current != null ? current.GetHashCode() : 0);
    }

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

代码看起来有点丑，但是这个结构体的用法很有代表性。

Colors color1 = Colors.Red;
Console.WriteLine(color1); // #ff0000

Colors color2 = (Colors) "#00ff00";
Console.WriteLine(color2); // #00ff00

// Colors color3 = "#0000ff"; // Compilation error
// String color4 = Colors.Red; // Compilation error

Colors color5 = (Colors)"#ff0000";
Console.WriteLine(color1 == color5); // True

Colors color6 = (Colors)"#00ff00";
Console.WriteLine(color1 == color6); // False

此外，我认为，如果需要大量这样的枚举，可能会使用代码生成(例如T4)。

2012-02-01 16:00:37

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