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

我创建了一个基类，用于在. net中创建字符串值的枚举。它只是一个c#文件，你可以复制粘贴到你的项目中，或者通过名为StringEnum的NuGet包安装。GitHub回购

如果类被注释为xml comment <completitionlist>，智能感知将提示枚举名称。(适用于c#和VB)

类似于普通enum的用法:

///<completionlist cref="HexColor"/> 
class HexColor : StringEnum<HexColor>
{
    public static readonly HexColor Blue = Create("#FF0000");
    public static readonly HexColor Green = Create("#00FF00");
    public static readonly HexColor Red = Create("#000FF");
}

    // Static Parse Method
    HexColor.Parse("#FF0000") // => HexColor.Red
    HexColor.Parse("#ff0000", caseSensitive: false) // => HexColor.Red
    HexColor.Parse("invalid") // => throws InvalidOperationException

    // Static TryParse method.
    HexColor.TryParse("#FF0000") // => HexColor.Red
    HexColor.TryParse("#ff0000", caseSensitive: false) // => HexColor.Red
    HexColor.TryParse("invalid") // => null

    // Parse and TryParse returns the preexistent instances
    object.ReferenceEquals(HexColor.Parse("#FF0000"), HexColor.Red) // => true

    // Conversion from your `StringEnum` to `string`
    string myString1 = HexColor.Red.ToString(); // => "#FF0000"
    string myString2 = HexColor.Red; // => "#FF0000" (implicit cast)

Instalation:

将下面的StringEnum基类粘贴到项目中。(最新版本) 或者安装StringEnum NuGet包，它基于。net Standard 1.0，所以它可以运行在。net Core >= 1.0， . net Framework >= 4.5, Mono >= 4.6等等。

    /// <summary>
    /// Base class for creating string-valued enums in .NET.<br/>
    /// Provides static Parse() and TryParse() methods and implicit cast to string.
    /// </summary>
    /// <example> 
    /// <code>
    /// class Color : StringEnum &lt;Color&gt;
    /// {
    ///     public static readonly Color Blue = Create("Blue");
    ///     public static readonly Color Red = Create("Red");
    ///     public static readonly Color Green = Create("Green");
    /// }
    /// </code>
    /// </example>
    /// <typeparam name="T">The string-valued enum type. (i.e. class Color : StringEnum&lt;Color&gt;)</typeparam>
    public abstract class StringEnum<T> : IEquatable<T> where T : StringEnum<T>, new()
    {
        protected string Value;
        private static Dictionary<string, T> valueDict = new Dictionary<string, T>();
        protected static T Create(string value)
        {
            if (value == null)
                return null; // the null-valued instance is null.

            var result = new T() { Value = value };
            valueDict.Add(value, result);
            return result;
        }

        public static implicit operator string(StringEnum<T> enumValue) => enumValue.Value;
        public override string ToString() => Value;

        public static bool operator !=(StringEnum<T> o1, StringEnum<T> o2) => o1?.Value != o2?.Value;
        public static bool operator ==(StringEnum<T> o1, StringEnum<T> o2) => o1?.Value == o2?.Value;

        public override bool Equals(object other) => this.Value.Equals((other as T)?.Value ?? (other as string));
        bool IEquatable<T>.Equals(T other) => this.Value.Equals(other.Value);
        public override int GetHashCode() => Value.GetHashCode();

        /// <summary>
        /// Parse the <paramref name="value"/> specified and returns a valid <typeparamref name="T"/> or else throws InvalidOperationException.
        /// </summary>
        /// <param name="value">The string value representad by an instance of <typeparamref name="T"/>. Matches by string value, not by the member name.</param>
        /// <param name="caseSensitive">If true, the strings must match case and takes O(log n). False allows different case but is little bit slower (O(n))</param>
        public static T Parse(string value, bool caseSensitive = true)
        {
            var result = TryParse(value, caseSensitive);
            if (result == null)
                throw new InvalidOperationException((value == null ? "null" : $"'{value}'") + $" is not a valid {typeof(T).Name}");

            return result;
        }

        /// <summary>
        /// Parse the <paramref name="value"/> specified and returns a valid <typeparamref name="T"/> or else returns null.
        /// </summary>
        /// <param name="value">The string value representad by an instance of <typeparamref name="T"/>. Matches by string value, not by the member name.</param>
        /// <param name="caseSensitive">If true, the strings must match case. False allows different case but is slower: O(n)</param>
        public static T TryParse(string value, bool caseSensitive = true)
        {
            if (value == null) return null;
            if (valueDict.Count == 0) System.Runtime.CompilerServices.RuntimeHelpers.RunClassConstructor(typeof(T).TypeHandle); // force static fields initialization
            if (caseSensitive)
            {
                if (valueDict.TryGetValue(value, out T item))
                    return item;
                else
                    return null;
            }
            else
            {
                // slower O(n) case insensitive search
                return valueDict.FirstOrDefault(f => f.Key.Equals(value, StringComparison.OrdinalIgnoreCase)).Value;
                // Why Ordinal? => https://esmithy.net/2007/10/15/why-stringcomparisonordinal-is-usually-the-right-choice/
            }
        }
    }

2019-10-24 04:01:43

其他回答

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

Enum.GetName(typeof(MyEnum), (int)MyEnum.FORMS)
Enum.GetName(typeof(MyEnum), (int)MyEnum.WINDOWSAUTHENTICATION)
Enum.GetName(typeof(MyEnum), (int)MyEnum.SINGLESIGNON)

输出是:

“形式”

“WINDOWSAUTHENTICATION”

“SINGLESIGNON”

2019-04-10 09:14:24

老帖子，但是…

这个问题的答案其实很简单。使用enumel . tostring()函数

这个函数有6个重载，你可以使用enumenumtostring ("F")或enumenumtostring()来返回字符串值。没必要为其他事操心。这是一个正在运行的演示

注意，这个解决方案可能不适用于所有编译器(这个演示没有像预期的那样工作)，但至少它适用于最新的编译器。

2016-10-03 07:33:49

使用对象枚举. parse(系统。类型枚举类型，字符串值，bool ignoreCase);从http://blogs.msdn.com/b/tims/archive/2004/04/02/106310.aspx获取

2011-08-18 19:29:54

我发现的Enums国际化或从各自的资源文件获取Enums文本的方法是通过继承DescriptionAttribute类创建一个属性类

public class EnumResourceAttribute : DescriptionAttribute
{

    public Type ResourceType { get; private set; }
    public string ResourceName { get; private set; }
    public int SortOrder { get; private set; }
    public EnumResourceAttribute(Type ResourceType,
                         string ResourceName,
                         int SortOrder)
    {

        this.ResourceType = ResourceType;
        this.ResourceName = ResourceName;
        this.SortOrder = SortOrder;
    }
}

创建另一个Static类，为GetString和GetString提供扩展方法。

public static class EnumHelper
{
    public static string GetString(this Enum value)
    {
        EnumResourceAttribute ea =
       (EnumResourceAttribute)value.GetType().GetField(value.ToString())
        .GetCustomAttributes(typeof(EnumResourceAttribute), false)
         .FirstOrDefault();
        if (ea != null)
        {
            PropertyInfo pi = ea.ResourceType
             .GetProperty(CommonConstants.ResourceManager);
            if (pi != null)
            {
                ResourceManager rm = (ResourceManager)pi
                .GetValue(null, null);
                return rm.GetString(ea.ResourceName);
            }

        }
        return string.Empty;
    }


    public static IList GetStrings(this Type enumType)
    {
        List<string> stringList = new List<string>();
        FieldInfo[] fiArray = enumType.GetFields();
        foreach (FieldInfo fi in fiArray)
        {
            EnumResourceAttribute ea =
                (EnumResourceAttribute)fi
                     .GetCustomAttributes(typeof(EnumResourceAttribute), false)
                     .FirstOrDefault();
            if (ea != null)
            {
                PropertyInfo pi = ea.ResourceType
                                    .GetProperty(CommonConstants.ResourceManager);
                if (pi != null)
                {
                    ResourceManager rm = (ResourceManager)pi
                                          .GetValue(null, null);
                    stringList.Add(rm.GetString(ea.ResourceName));
                }
            }
        }
        return stringList.ToList();
    }
}

在Enum的元素上，你可以这样写:

public enum Priority
{
     [EnumResourceAttribute(typeof(Resources.AdviceModule), Resources.ResourceNames.AdviceCreateAdviceExternaPriorityMemberHigh, 1)]
    High,
     [EnumResourceAttribute(typeof(Resources.AdviceModule), Resources.ResourceNames.AdviceCreateAdviceExternaPriorityMemberRoutine, 2)]
    Routine
}

Where Resources.ResourceNames.AdviceCreateAdviceExternaPriorityMemberHigh & resources . resourcename . advicecreateadviceexternaprioritymemberroutine是资源文件中的常量，或者你可以说字符串，其值可以在不同的文化中可用。

如果你在MVC架构中实现你的web应用程序，那么创建一个属性

private IList result;
public IList Result
{
    get
    {
        result = typeof(Priority).GetStrings();
        return result;
    }
}

在你的.cshtml文件中，你可以像这样将枚举绑定到你的下拉列表:

@Html.DropDownListFor(model => Model.vwClinicalInfo.Priority, new SelectList(Model.Result))

谢谢 Ratnesh

2011-09-27 10:19:49

Enum的字符串表示形式

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