当前位置：文江博客话题详情

C# integer casting enums

如何在 C# 中将 int 转换为 enum？

发布于 2024-07-04 14:22:51 字数 56 浏览 6 评论 0原文

如何在 C# 中将 int 转换为 enum？

收藏 0

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

扫码二维码加入Web技术交流群

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

评论（30）

娇俏 2024-07-11 14:22:52

就我而言，我需要从 WCF 服务返回枚举。我还需要一个友好的名称，而不仅仅是 enum.ToString()。

这是我的 WCF 课程。

[DataContract]
public class EnumMember
{
    [DataMember]
    public string Description { get; set; }

    [DataMember]
    public int Value { get; set; }

    public static List<EnumMember> ConvertToList<T>()
    {
        Type type = typeof(T);

        if (!type.IsEnum)
        {
            throw new ArgumentException("T must be of type enumeration.");
        }

        var members = new List<EnumMember>();

        foreach (string item in System.Enum.GetNames(type))
        {
            var enumType = System.Enum.Parse(type, item);

            members.Add(
                new EnumMember() { Description = enumType.GetDescriptionValue(), Value = ((IConvertible)enumType).ToInt32(null) });
        }

        return members;
    }
}

这是从枚举获取描述的扩展方法。

    public static string GetDescriptionValue<T>(this T source)
    {
        FieldInfo fileInfo = source.GetType().GetField(source.ToString());
        DescriptionAttribute[] attributes = (DescriptionAttribute[])fileInfo.GetCustomAttributes(typeof(DescriptionAttribute), false);            

        if (attributes != null && attributes.Length > 0)
        {
            return attributes[0].Description;
        }
        else
        {
            return source.ToString();
        }
    }

执行：

return EnumMember.ConvertToList<YourType>();

In my case, I needed to return the enum from a WCF service. I also needed a friendly name, not just the enum.ToString().

Here's my WCF Class.

[DataContract]
public class EnumMember
{
    [DataMember]
    public string Description { get; set; }

    [DataMember]
    public int Value { get; set; }

    public static List<EnumMember> ConvertToList<T>()
    {
        Type type = typeof(T);

        if (!type.IsEnum)
        {
            throw new ArgumentException("T must be of type enumeration.");
        }

        var members = new List<EnumMember>();

        foreach (string item in System.Enum.GetNames(type))
        {
            var enumType = System.Enum.Parse(type, item);

            members.Add(
                new EnumMember() { Description = enumType.GetDescriptionValue(), Value = ((IConvertible)enumType).ToInt32(null) });
        }

        return members;
    }
}

Here's the Extension method that gets the Description from the Enum.

    public static string GetDescriptionValue<T>(this T source)
    {
        FieldInfo fileInfo = source.GetType().GetField(source.ToString());
        DescriptionAttribute[] attributes = (DescriptionAttribute[])fileInfo.GetCustomAttributes(typeof(DescriptionAttribute), false);            

        if (attributes != null && attributes.Length > 0)
        {
            return attributes[0].Description;
        }
        else
        {
            return source.ToString();
        }
    }

Implementation:

return EnumMember.ConvertToList<YourType>();

回复收藏 0 原文

妄断弥空 2024-07-11 14:22:52

它可以帮助您将任何输入数据转换为用户所需的枚举。假设您有一个如下所示的枚举，默认情况下为 int。请在枚举的开头添加一个默认值。当未找到与输入值匹配的情况时，在辅助方法中使用该方法。

public enum FriendType  
{
    Default,
    Audio,
    Video,
    Image
}

public static class EnumHelper<T>
{
    public static T ConvertToEnum(dynamic value)
    {
        var result = default(T);
        var tempType = 0;

        //see Note below
        if (value != null &&
            int.TryParse(value.ToString(), out  tempType) && 
            Enum.IsDefined(typeof(T), tempType))
        {
            result = (T)Enum.ToObject(typeof(T), tempType); 
        }
        return result;
    }
}

NB：这里我尝试将值解析为int，因为枚举默认是int
如果您像这样定义枚举，它是 byte 类型。

public enum MediaType : byte
{
    Default,
    Audio,
    Video,
    Image
}

您需要将辅助方法的解析从

int.TryParse(value.ToString(), out  tempType)

byte.TryParse(value.ToString(), out tempType)

我检查我的方法以获取以下输入，

EnumHelper<FriendType>.ConvertToEnum(null);
EnumHelper<FriendType>.ConvertToEnum("");
EnumHelper<FriendType>.ConvertToEnum("-1");
EnumHelper<FriendType>.ConvertToEnum("6");
EnumHelper<FriendType>.ConvertToEnum("");
EnumHelper<FriendType>.ConvertToEnum("2");
EnumHelper<FriendType>.ConvertToEnum(-1);
EnumHelper<FriendType>.ConvertToEnum(0);
EnumHelper<FriendType>.ConvertToEnum(1);
EnumHelper<FriendType>.ConvertToEnum(9);

抱歉我的英语

It can help you to convert any input data to user desired enum. Suppose you have an enum like below which by default int. Please add a Default value at first of your enum. Which is used at helpers medthod when there is no match found with input value.

public enum FriendType  
{
    Default,
    Audio,
    Video,
    Image
}

public static class EnumHelper<T>
{
    public static T ConvertToEnum(dynamic value)
    {
        var result = default(T);
        var tempType = 0;

        //see Note below
        if (value != null &&
            int.TryParse(value.ToString(), out  tempType) && 
            Enum.IsDefined(typeof(T), tempType))
        {
            result = (T)Enum.ToObject(typeof(T), tempType); 
        }
        return result;
    }
}

N.B: Here I try to parse value into int, because enum is by default int
If you define enum like this which is byte type.

public enum MediaType : byte
{
    Default,
    Audio,
    Video,
    Image
}

You need to change parsing at helper method from

int.TryParse(value.ToString(), out  tempType)

to

byte.TryParse(value.ToString(), out tempType)

I check my method for following inputs

EnumHelper<FriendType>.ConvertToEnum(null);
EnumHelper<FriendType>.ConvertToEnum("");
EnumHelper<FriendType>.ConvertToEnum("-1");
EnumHelper<FriendType>.ConvertToEnum("6");
EnumHelper<FriendType>.ConvertToEnum("");
EnumHelper<FriendType>.ConvertToEnum("2");
EnumHelper<FriendType>.ConvertToEnum(-1);
EnumHelper<FriendType>.ConvertToEnum(0);
EnumHelper<FriendType>.ConvertToEnum(1);
EnumHelper<FriendType>.ConvertToEnum(9);

sorry for my english

回复收藏 0 原文

等你爱我 2024-07-11 14:22:52

您可以使用扩展方法。

public static class Extensions
{

    public static T ToEnum<T>(this string data) where T : struct
    {
        if (!Enum.TryParse(data, true, out T enumVariable))
        {
            if (Enum.IsDefined(typeof(T), enumVariable))
            {
                return enumVariable;
            }
        }

        return default;
    }

    public static T ToEnum<T>(this int data) where T : struct
    {
        return (T)Enum.ToObject(typeof(T), data);
    }
}

像下面的代码一样使用它：

枚举：

public enum DaysOfWeeks
{
    Monday = 1,
    Tuesday = 2,
    Wednesday = 3,
    Thursday = 4,
    Friday = 5,
    Saturday = 6,
    Sunday = 7,
}

用法：

 string Monday = "Mon";
 int Wednesday = 3;
 var Mon = Monday.ToEnum<DaysOfWeeks>();
 var Wed = Wednesday.ToEnum<DaysOfWeeks>();

You can use an extension method.

public static class Extensions
{

    public static T ToEnum<T>(this string data) where T : struct
    {
        if (!Enum.TryParse(data, true, out T enumVariable))
        {
            if (Enum.IsDefined(typeof(T), enumVariable))
            {
                return enumVariable;
            }
        }

        return default;
    }

    public static T ToEnum<T>(this int data) where T : struct
    {
        return (T)Enum.ToObject(typeof(T), data);
    }
}

Use it like the below code:

Enum:

public enum DaysOfWeeks
{
    Monday = 1,
    Tuesday = 2,
    Wednesday = 3,
    Thursday = 4,
    Friday = 5,
    Saturday = 6,
    Sunday = 7,
}

Usage:

 string Monday = "Mon";
 int Wednesday = 3;
 var Mon = Monday.ToEnum<DaysOfWeeks>();
 var Wed = Wednesday.ToEnum<DaysOfWeeks>();

回复收藏 0 原文

初懵 2024-07-11 14:22:52

我更喜欢使用可为空的枚举类型变量的简短方法。

var enumValue = (MyEnum?)enumInt;

if (!enumValue.HasValue)
{
    throw new ArgumentException(nameof(enumValue));
}

I prefer a short way using a nullable enum type variable.

var enumValue = (MyEnum?)enumInt;

if (!enumValue.HasValue)
{
    throw new ArgumentException(nameof(enumValue));
}

回复收藏 0 原文

星 2024-07-11 14:22:52

您只需使用显式转换将 int 转换为 enum 或 enum 转换为 int

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine((int)Number.three); //Output=3

        Console.WriteLine((Number)3);// Outout three
        Console.Read();
    }

    public enum Number
    {
        Zero = 0,
        One = 1,
        Two = 2,
        three = 3
    }
}

You simply use Explicit conversion Cast int to enum or enum to int

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine((int)Number.three); //Output=3

        Console.WriteLine((Number)3);// Outout three
        Console.Read();
    }

    public enum Number
    {
        Zero = 0,
        One = 1,
        Two = 2,
        three = 3
    }
}

回复收藏 0 原文

乱世争霸 2024-07-11 14:22:52

我不知道从哪里得到这个枚举扩展的部分，但它来自 stackoverflow。对此我感到很抱歉！但我采用了这个并将其修改为带有标志的枚举。
对于带有标志的枚举，我这样做了：

  public static class Enum<T> where T : struct
  {
     private static readonly IEnumerable<T> All = Enum.GetValues(typeof (T)).Cast<T>();
     private static readonly Dictionary<int, T> Values = All.ToDictionary(k => Convert.ToInt32(k));

     public static T? CastOrNull(int value)
     {
        T foundValue;
        if (Values.TryGetValue(value, out foundValue))
        {
           return foundValue;
        }

        // For enums with Flags-Attribut.
        try
        {
           bool isFlag = typeof(T).GetCustomAttributes(typeof(FlagsAttribute), false).Length > 0;
           if (isFlag)
           {
              int existingIntValue = 0;

              foreach (T t in Enum.GetValues(typeof(T)))
              {
                 if ((value & Convert.ToInt32(t)) > 0)
                 {
                    existingIntValue |= Convert.ToInt32(t);
                 }
              }
              if (existingIntValue == 0)
              {
                 return null;
              }

              return (T)(Enum.Parse(typeof(T), existingIntValue.ToString(), true));
           }
        }
        catch (Exception)
        {
           return null;
        }
        return null;
     }
  }

示例：

[Flags]
public enum PetType
{
  None = 0, Dog = 1, Cat = 2, Fish = 4, Bird = 8, Reptile = 16, Other = 32
};

integer values 
1=Dog;
13= Dog | Fish | Bird;
96= Other;
128= Null;

I don't know anymore where I get the part of this enum extension, but it is from stackoverflow. I am sorry for this! But I took this one and modified it for enums with Flags.
For enums with Flags I did this:

  public static class Enum<T> where T : struct
  {
     private static readonly IEnumerable<T> All = Enum.GetValues(typeof (T)).Cast<T>();
     private static readonly Dictionary<int, T> Values = All.ToDictionary(k => Convert.ToInt32(k));

     public static T? CastOrNull(int value)
     {
        T foundValue;
        if (Values.TryGetValue(value, out foundValue))
        {
           return foundValue;
        }

        // For enums with Flags-Attribut.
        try
        {
           bool isFlag = typeof(T).GetCustomAttributes(typeof(FlagsAttribute), false).Length > 0;
           if (isFlag)
           {
              int existingIntValue = 0;

              foreach (T t in Enum.GetValues(typeof(T)))
              {
                 if ((value & Convert.ToInt32(t)) > 0)
                 {
                    existingIntValue |= Convert.ToInt32(t);
                 }
              }
              if (existingIntValue == 0)
              {
                 return null;
              }

              return (T)(Enum.Parse(typeof(T), existingIntValue.ToString(), true));
           }
        }
        catch (Exception)
        {
           return null;
        }
        return null;
     }
  }

Example:

[Flags]
public enum PetType
{
  None = 0, Dog = 1, Cat = 2, Fish = 4, Bird = 8, Reptile = 16, Other = 32
};

integer values 
1=Dog;
13= Dog | Fish | Bird;
96= Other;
128= Null;

回复收藏 0 原文

锦爱 2024-07-11 14:22:52

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace SamplePrograme
{
    public class Program
    {
        public enum Suit : int
        {
            Spades = 0,
            Hearts = 1,
            Clubs = 2,
            Diamonds = 3
        }

        public static void Main(string[] args)
        {
            //from string
            Console.WriteLine((Suit) Enum.Parse(typeof(Suit), "Clubs"));

            //from int
            Console.WriteLine((Suit)1);

            //From number you can also
            Console.WriteLine((Suit)Enum.ToObject(typeof(Suit) ,1));
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace SamplePrograme
{
    public class Program
    {
        public enum Suit : int
        {
            Spades = 0,
            Hearts = 1,
            Clubs = 2,
            Diamonds = 3
        }

        public static void Main(string[] args)
        {
            //from string
            Console.WriteLine((Suit) Enum.Parse(typeof(Suit), "Clubs"));

            //from int
            Console.WriteLine((Suit)1);

            //From number you can also
            Console.WriteLine((Suit)Enum.ToObject(typeof(Suit) ,1));
        }
    }
}

回复收藏 0 原文

马蹄踏│碎落叶 2024-07-11 14:22:52

您只需执行以下操作：

int intToCast = 1;
TargetEnum f = (TargetEnum) intToCast ;

要确保只转换正确的值，否则可以抛出异常：

int intToCast = 1;
if (Enum.IsDefined(typeof(TargetEnum), intToCast ))
{
    TargetEnum target = (TargetEnum)intToCast ;
}
else
{
   // Throw your exception.
}

请注意，使用 IsDefined 的成本很高，甚至不仅仅是转换，因此取决于您的实现来决定使用它还是不是。

You just do like below:

int intToCast = 1;
TargetEnum f = (TargetEnum) intToCast ;

To make sure that you only cast the right values and that you can throw an exception otherwise:

int intToCast = 1;
if (Enum.IsDefined(typeof(TargetEnum), intToCast ))
{
    TargetEnum target = (TargetEnum)intToCast ;
}
else
{
   // Throw your exception.
}

Note that using IsDefined is costly and even more than just casting, so it depends on your implementation to decide to use it or not.

回复收藏 0 原文

凶凌 2024-07-11 14:22:52

转换与 Enum 的不同方式

enum orientation : byte
{
 north = 1,
 south = 2,
 east = 3,
 west = 4
}

class Program
{
  static void Main(string[] args)
  {
    orientation myDirection = orientation.north;
    Console.WriteLine(“myDirection = {0}”, myDirection); //output myDirection =north
    Console.WriteLine((byte)myDirection); //output 1

    string strDir = Convert.ToString(myDirection);
        Console.WriteLine(strDir); //output north

    string myString = “north”; //to convert string to Enum
    myDirection = (orientation)Enum.Parse(typeof(orientation),myString);


 }
}

Different ways to cast to and from Enum

enum orientation : byte
{
 north = 1,
 south = 2,
 east = 3,
 west = 4
}

class Program
{
  static void Main(string[] args)
  {
    orientation myDirection = orientation.north;
    Console.WriteLine(“myDirection = {0}”, myDirection); //output myDirection =north
    Console.WriteLine((byte)myDirection); //output 1

    string strDir = Convert.ToString(myDirection);
        Console.WriteLine(strDir); //output north

    string myString = “north”; //to convert string to Enum
    myDirection = (orientation)Enum.Parse(typeof(orientation),myString);


 }
}

回复收藏 0 原文

小傻瓜 2024-07-11 14:22:52

在 C# 中将 int 转换为 enum 的简单明了的方法：

public class Program
{
    public enum Color : int
    {
        Blue   = 0,
        Black  = 1,
        Green  = 2,
        Gray   = 3,
        Yellow = 4
    }

    public static void Main(string[] args)
    {
        // From string
        Console.WriteLine((Color) Enum.Parse(typeof(Color), "Green"));

        // From int
        Console.WriteLine((Color)2);

        // From number you can also
        Console.WriteLine((Color)Enum.ToObject(typeof(Color), 2));
    }
}

The easy and clear way for casting an int to enum in C#:

public class Program
{
    public enum Color : int
    {
        Blue   = 0,
        Black  = 1,
        Green  = 2,
        Gray   = 3,
        Yellow = 4
    }

    public static void Main(string[] args)
    {
        // From string
        Console.WriteLine((Color) Enum.Parse(typeof(Color), "Green"));

        // From int
        Console.WriteLine((Color)2);

        // From number you can also
        Console.WriteLine((Color)Enum.ToObject(typeof(Color), 2));
    }
}

回复收藏 0 原文

扎心 2024-07-11 14:22:51

下面是将 Int32 转换为 Enum 的扩展方法。

即使该值高于可能的最大值，它也会遵循按位标志。例如，如果您有一个可能为 1、2 和 4 的枚举，但 int 为 9，如果没有 8，它会将其理解为 1。这使您可以在代码更新之前更新数据。

   public static TEnum ToEnum<TEnum>(this int val) where TEnum : struct, IComparable, IFormattable, IConvertible
    {
        if (!typeof(TEnum).IsEnum)
        {
            return default(TEnum);
        }

        if (Enum.IsDefined(typeof(TEnum), val))
        {//if a straightforward single value, return that
            return (TEnum)Enum.ToObject(typeof(TEnum), val);
        }

        var candidates = Enum
            .GetValues(typeof(TEnum))
            .Cast<int>()
            .ToList();

        var isBitwise = candidates
            .Select((n, i) => {
                if (i < 2) return n == 0 || n == 1;
                return n / 2 == candidates[i - 1];
            })
            .All(y => y);

        var maxPossible = candidates.Sum();

        if (
            Enum.TryParse(val.ToString(), out TEnum asEnum)
            && (val <= maxPossible || !isBitwise)
        ){//if it can be parsed as a bitwise enum with multiple flags,
          //or is not bitwise, return the result of TryParse
            return asEnum;
        }

        //If the value is higher than all possible combinations,
        //remove the high imaginary values not accounted for in the enum
        var excess = Enumerable
            .Range(0, 32)
            .Select(n => (int)Math.Pow(2, n))
            .Where(n => n <= val && n > 0 && !candidates.Contains(n))
            .Sum();

        return Enum.TryParse((val - excess).ToString(), out asEnum) ? asEnum : default(TEnum);
    }

Here's an extension method that casts Int32 to Enum.

It honors bitwise flags even when the value is higher than the maximum possible. For example if you have an enum with possibilities 1, 2, and 4, but the int is 9, it understands that as 1 in absence of an 8. This lets you make data updates ahead of code updates.

   public static TEnum ToEnum<TEnum>(this int val) where TEnum : struct, IComparable, IFormattable, IConvertible
    {
        if (!typeof(TEnum).IsEnum)
        {
            return default(TEnum);
        }

        if (Enum.IsDefined(typeof(TEnum), val))
        {//if a straightforward single value, return that
            return (TEnum)Enum.ToObject(typeof(TEnum), val);
        }

        var candidates = Enum
            .GetValues(typeof(TEnum))
            .Cast<int>()
            .ToList();

        var isBitwise = candidates
            .Select((n, i) => {
                if (i < 2) return n == 0 || n == 1;
                return n / 2 == candidates[i - 1];
            })
            .All(y => y);

        var maxPossible = candidates.Sum();

        if (
            Enum.TryParse(val.ToString(), out TEnum asEnum)
            && (val <= maxPossible || !isBitwise)
        ){//if it can be parsed as a bitwise enum with multiple flags,
          //or is not bitwise, return the result of TryParse
            return asEnum;
        }

        //If the value is higher than all possible combinations,
        //remove the high imaginary values not accounted for in the enum
        var excess = Enumerable
            .Range(0, 32)
            .Select(n => (int)Math.Pow(2, n))
            .Where(n => n <= val && n > 0 && !candidates.Contains(n))
            .Sum();

        return Enum.TryParse((val - excess).ToString(), out asEnum) ? asEnum : default(TEnum);
    }

回复收藏 0 原文

﹏半生如梦愿梦如真 2024-07-11 14:22:51

对于字符串，您可以执行以下操作：

var result = Enum.TryParse(typeof(MyEnum), yourString, out yourEnum)

并确保检查结果以确定转换是否失败。

对于 int，您可以执行以下操作：

MyEnum someValue = (MyEnum)myIntValue;

For string, you can do the following:

var result = Enum.TryParse(typeof(MyEnum), yourString, out yourEnum)

And make sure to check the result to determine if the conversion failed.

For int, you can do the following:

MyEnum someValue = (MyEnum)myIntValue;

回复收藏 0 原文

心头的小情儿 2024-07-11 14:22:51

下面是一个很好的枚举实用程序类

public static class EnumHelper
{
    public static int[] ToIntArray<T>(T[] value)
    {
        int[] result = new int[value.Length];
        for (int i = 0; i < value.Length; i++)
            result[i] = Convert.ToInt32(value[i]);
        return result;
    }

    public static T[] FromIntArray<T>(int[] value) 
    {
        T[] result = new T[value.Length];
        for (int i = 0; i < value.Length; i++)
            result[i] = (T)Enum.ToObject(typeof(T),value[i]);
        return result;
    }


    internal static T Parse<T>(string value, T defaultValue)
    {
        if (Enum.IsDefined(typeof(T), value))
            return (T) Enum.Parse(typeof (T), value);

        int num;
        if(int.TryParse(value,out num))
        {
            if (Enum.IsDefined(typeof(T), num))
                return (T)Enum.ToObject(typeof(T), num);
        }

        return defaultValue;
    }
}

Below is a nice utility class for Enums

public static class EnumHelper
{
    public static int[] ToIntArray<T>(T[] value)
    {
        int[] result = new int[value.Length];
        for (int i = 0; i < value.Length; i++)
            result[i] = Convert.ToInt32(value[i]);
        return result;
    }

    public static T[] FromIntArray<T>(int[] value) 
    {
        T[] result = new T[value.Length];
        for (int i = 0; i < value.Length; i++)
            result[i] = (T)Enum.ToObject(typeof(T),value[i]);
        return result;
    }


    internal static T Parse<T>(string value, T defaultValue)
    {
        if (Enum.IsDefined(typeof(T), value))
            return (T) Enum.Parse(typeof (T), value);

        int num;
        if(int.TryParse(value,out num))
        {
            if (Enum.IsDefined(typeof(T), num))
                return (T)Enum.ToObject(typeof(T), num);
        }

        return defaultValue;
    }
}

回复收藏 0 原文

半﹌身腐败 2024-07-11 14:22:51

我正在使用这段代码将 int 转换为我的 enum：

if (typeof(YourEnum).IsEnumDefined(valueToCast))
    return (YourEnum)valueToCast;
else 
{
    // handle it here, if it is not defined
}

我发现它是最好的解决方案。

I am using this piece of code to cast int to my enum:

if (typeof(YourEnum).IsEnumDefined(valueToCast))
    return (YourEnum)valueToCast;
else 
{
    // handle it here, if it is not defined
}

I find it the best solution.

回复收藏 0 原文

鱼忆七猫命九 2024-07-11 14:22:51

举个例子：

int one = 1;
MyEnum e = (MyEnum)one;

Take the following example:

int one = 1;
MyEnum e = (MyEnum)one;

回复收藏 0 原文

情深如许 2024-07-11 14:22:51

我认为要获得完整的答案，人们必须了解枚举在 .NET 内部是如何工作的。

工作原理

.NET 中的枚举是一种将一组值（字段）映射到基本类型（默认为 int）的结构。但是，您实际上可以选择枚举映射到的整数类型：

public enum Foo : short

在这种情况下，枚举被映射到 short 数据类型，这意味着它将作为 Short 存储在内存中，并且行为如下当您施放并使用它时会出现短路。

如果从 IL 的角度来看，(normal, int) 枚举看起来像这样：

.class public auto ansi serializable sealed BarFlag extends System.Enum
{
    .custom instance void System.FlagsAttribute::.ctor()
    .custom instance void ComVisibleAttribute::.ctor(bool) = { bool(true) }

    .field public static literal valuetype BarFlag AllFlags = int32(0x3fff)
    .field public static literal valuetype BarFlag Foo1 = int32(1)
    .field public static literal valuetype BarFlag Foo2 = int32(0x2000)

    // and so on for all flags or enum values

    .field public specialname rtspecialname int32 value__
}

这里应该引起您注意的是 value__ 与枚举值分开存储。在上面的枚举 Foo 中，value__ 的类型是 int16。这基本上意味着您可以在枚举中存储您想要的任何内容，只要类型匹配。

此时我想指出 System.Enum 是一个值类型，这基本上意味着 BarFlag 将占用内存中的 4 个字节，而 Foo 将占用 2 —— 例如底层类型的大小（实际上比这更复杂，但是嘿......）。

答案

因此，如果您有一个整数想要映射到枚举，则运行时只需执行两件事：复制 4 个字节并将其命名为其他名称（枚举的名称）。复制是隐式的，因为数据存储为值类型 - 这基本上意味着，如果您使用非托管代码，您可以简单地交换枚举和整数，而无需复制数据。

为了安全起见，我认为最好的做法是知道基础类型是相同的或隐式可转换的并确保枚举值存在（默认情况下不检查它们！）。

要了解其工作原理，请尝试以下代码：

public enum MyEnum : int
{
    Foo = 1,
    Bar = 2,
    Mek = 5
}

static void Main(string[] args)
{
    var e1 = (MyEnum)5;
    var e2 = (MyEnum)6;

    Console.WriteLine("{0} {1}", e1, e2);
    Console.ReadLine();
}

请注意，转换为 e2 也可以！从上面的编译器角度来看，这是有道理的：当 Console.WriteLine 调用 ToString() 时，value__ 字段简单地填充为 5 或 6。，e1 的名称已解析，而 e2 的名称未解析。

如果这不是您想要的，请使用 Enum.IsDefined(typeof(MyEnum), 6) 检查您要转换的值是否映射到已定义的枚举。

另请注意，我明确说明了枚举的基础类型，即使编译器实际上会检查这一点。我这样做是为了确保我不会在未来遇到任何意外。要查看这些惊喜的实际效果，您可以使用以下代码（实际上我在数据库代码中经常看到这种情况发生）：

public enum MyEnum : short
{
    Mek = 5
}

static void Main(string[] args)
{
    var e1 = (MyEnum)32769; // will not compile, out of bounds for a short

    object o = 5;
    var e2 = (MyEnum)o;     // will throw at runtime, because o is of type int

    Console.WriteLine("{0} {1}", e1, e2);
    Console.ReadLine();
}

I think to get a complete answer, people have to know how enums work internally in .NET.

How stuff works

An enum in .NET is a structure that maps a set of values (fields) to a basic type (the default is int). However, you can actually choose the integral type that your enum maps to:

public enum Foo : short

In this case the enum is mapped to the short data type, which means it will be stored in memory as a short and will behave as a short when you cast and use it.

If you look at it from a IL point of view, a (normal, int) enum looks like this:

.class public auto ansi serializable sealed BarFlag extends System.Enum
{
    .custom instance void System.FlagsAttribute::.ctor()
    .custom instance void ComVisibleAttribute::.ctor(bool) = { bool(true) }

    .field public static literal valuetype BarFlag AllFlags = int32(0x3fff)
    .field public static literal valuetype BarFlag Foo1 = int32(1)
    .field public static literal valuetype BarFlag Foo2 = int32(0x2000)

    // and so on for all flags or enum values

    .field public specialname rtspecialname int32 value__
}

What should get your attention here is that the value__ is stored separately from the enum values. In the case of the enum Foo above, the type of value__ is int16. This basically means that you can store whatever you want in an enum, as long as the types match.

At this point I'd like to point out that System.Enum is a value type, which basically means that BarFlag will take up 4 bytes in memory and Foo will take up 2 -- e.g. the size of the underlying type (it's actually more complicated than that, but hey...).

The answer

So, if you have an integer that you want to map to an enum, the runtime only has to do 2 things: copy the 4 bytes and name it something else (the name of the enum). Copying is implicit because the data is stored as value type - this basically means that if you use unmanaged code, you can simply interchange enums and integers without copying data.

To make it safe, I think it's a best practice to know that the underlying types are the same or implicitly convertible and to ensure the enum values exist (they aren't checked by default!).

To see how this works, try the following code:

public enum MyEnum : int
{
    Foo = 1,
    Bar = 2,
    Mek = 5
}

static void Main(string[] args)
{
    var e1 = (MyEnum)5;
    var e2 = (MyEnum)6;

    Console.WriteLine("{0} {1}", e1, e2);
    Console.ReadLine();
}

Note that casting to e2 also works! From the compiler perspective above this makes sense: the value__ field is simply filled with either 5 or 6 and when Console.WriteLine calls ToString(), the name of e1 is resolved while the name of e2 is not.

If that's not what you intended, use Enum.IsDefined(typeof(MyEnum), 6) to check if the value you are casting maps to a defined enum.

Also note that I'm explicit about the underlying type of the enum, even though the compiler actually checks this. I'm doing this to ensure I don't run into any surprises down the road. To see these surprises in action, you can use the following code (actually I've seen this happen a lot in database code):

public enum MyEnum : short
{
    Mek = 5
}

static void Main(string[] args)
{
    var e1 = (MyEnum)32769; // will not compile, out of bounds for a short

    object o = 5;
    var e2 = (MyEnum)o;     // will throw at runtime, because o is of type int

    Console.WriteLine("{0} {1}", e1, e2);
    Console.ReadLine();
}

回复收藏 0 原文

来世叙缘 2024-07-11 14:22:51

或者，使用扩展方法而不是单行：

public static T ToEnum<T>(this string enumString)
{
    return (T) Enum.Parse(typeof (T), enumString);
}

用法：

Color colorEnum = "Red".ToEnum<Color>();

或

string color = "Red";
var colorEnum = color.ToEnum<Color>();

Alternatively, use an extension method instead of a one-liner:

public static T ToEnum<T>(this string enumString)
{
    return (T) Enum.Parse(typeof (T), enumString);
}

Usage:

Color colorEnum = "Red".ToEnum<Color>();

OR

string color = "Red";
var colorEnum = color.ToEnum<Color>();

回复收藏 0 原文

原来是傀儡 2024-07-11 14:22:51

只需转换它：

MyEnum e = (MyEnum)3;

使用 Enum 检查它是否在范围内。已定义：

if (Enum.IsDefined(typeof(MyEnum), 3)) { ... }

Just cast it:

MyEnum e = (MyEnum)3;

Check if it's in range using Enum.IsDefined:

if (Enum.IsDefined(typeof(MyEnum), 3)) { ... }

回复收藏 0 原文

牵你的手，一向走下去 2024-07-11 14:22:51

下面是一个稍微好一点的扩展方法：

public static string ToEnumString<TEnum>(this int enumValue)
{
    var enumString = enumValue.ToString();
    if (Enum.IsDefined(typeof(TEnum), enumValue))
    {
        enumString = ((TEnum) Enum.ToObject(typeof (TEnum), enumValue)).ToString();
    }
    return enumString;
}

The following is a slightly better extension method:

public static string ToEnumString<TEnum>(this int enumValue)
{
    var enumString = enumValue.ToString();
    if (Enum.IsDefined(typeof(TEnum), enumValue))
    {
        enumString = ((TEnum) Enum.ToObject(typeof (TEnum), enumValue)).ToString();
    }
    return enumString;
}

回复收藏 0 原文

骄兵必败 2024-07-11 14:22:51

这会使用 Tawani 的实用程序类。我用它来转换可能不完整的命令行开关变量。由于枚举不能为空，因此您在逻辑上应该提供一个默认值。可以这样调用：

var result = EnumParser<MyEnum>.Parse(valueToParse, MyEnum.FirstValue);

这是代码：

using System;

public class EnumParser<T> where T : struct
{
    public static T Parse(int toParse, T defaultVal)
    {
        return Parse(toParse + "", defaultVal);
    }
    public static T Parse(string toParse, T defaultVal)
    {
        T enumVal = defaultVal;
        if (defaultVal is Enum && !String.IsNullOrEmpty(toParse))
        {
            int index;
            if (int.TryParse(toParse, out index))
            {
                Enum.TryParse(index + "", out enumVal);
            }
            else
            {
                if (!Enum.TryParse<T>(toParse + "", true, out enumVal))
                {
                    MatchPartialName(toParse, ref enumVal);
                }
            }
        }
        return enumVal;
    }

    public static void MatchPartialName(string toParse, ref T enumVal)
    {
        foreach (string member in enumVal.GetType().GetEnumNames())
        {
            if (member.ToLower().Contains(toParse.ToLower()))
            {
                if (Enum.TryParse<T>(member + "", out enumVal))
                {
                    break;
                }
            }
        }
    }
}

仅供参考：问题是关于整数，没有人提到整数也会在 Enum.TryParse() 中显式转换

This parses integers or strings to a target enum with partial matching in .NET 4.0 using generics like in Tawani's utility class. I am using it to convert command-line switch variables which may be incomplete. Since an enum cannot be null, you should logically provide a default value. It can be called like this:

var result = EnumParser<MyEnum>.Parse(valueToParse, MyEnum.FirstValue);

Here's the code:

using System;

public class EnumParser<T> where T : struct
{
    public static T Parse(int toParse, T defaultVal)
    {
        return Parse(toParse + "", defaultVal);
    }
    public static T Parse(string toParse, T defaultVal)
    {
        T enumVal = defaultVal;
        if (defaultVal is Enum && !String.IsNullOrEmpty(toParse))
        {
            int index;
            if (int.TryParse(toParse, out index))
            {
                Enum.TryParse(index + "", out enumVal);
            }
            else
            {
                if (!Enum.TryParse<T>(toParse + "", true, out enumVal))
                {
                    MatchPartialName(toParse, ref enumVal);
                }
            }
        }
        return enumVal;
    }

    public static void MatchPartialName(string toParse, ref T enumVal)
    {
        foreach (string member in enumVal.GetType().GetEnumNames())
        {
            if (member.ToLower().Contains(toParse.ToLower()))
            {
                if (Enum.TryParse<T>(member + "", out enumVal))
                {
                    break;
                }
            }
        }
    }
}

FYI: The question was about integers, which nobody mentioned will also explicitly convert in Enum.TryParse()

回复收藏 0 原文

久隐师 2024-07-11 14:22:51

稍微偏离了原来的问题，但我找到了堆栈溢出问题的答案从枚举中获取 int 值有用。使用 public const int 属性创建一个静态类，使您可以轻松地将一堆相关的 int 常量收集在一起，然后不必将它们强制转换为 int< /code> 使用它们时。

public static class Question
{
    public static readonly int Role = 2;
    public static readonly int ProjectFunding = 3;
    public static readonly int TotalEmployee = 4;
    public static readonly int NumberOfServers = 5;
    public static readonly int TopBusinessConcern = 6;
}

显然，一些枚举类型的功能将会丢失，但对于存储一堆数据库 id 常量来说，这似乎是一个非常整洁的解决方案。

Slightly getting away from the original question, but I found an answer to Stack Overflow question Get int value from enum useful. Create a static class with public const int properties, allowing you to easily collect together a bunch of related int constants, and then not have to cast them to int when using them.

public static class Question
{
    public static readonly int Role = 2;
    public static readonly int ProjectFunding = 3;
    public static readonly int TotalEmployee = 4;
    public static readonly int NumberOfServers = 5;
    public static readonly int TopBusinessConcern = 6;
}

Obviously, some of the enum type functionality will be lost, but for storing a bunch of database id constants, it seems like a pretty tidy solution.

回复收藏 0 原文

晨与橙与城 2024-07-11 14:22:51

从 int：

YourEnum foo = (YourEnum)yourInt;

从字符串：

YourEnum foo = (YourEnum) Enum.Parse(typeof(YourEnum), yourString);

// The foo.ToString().Contains(",") check is necessary for 
// enumerations marked with a [Flags] attribute.
if (!Enum.IsDefined(typeof(YourEnum), foo) && !foo.ToString().Contains(","))
{
    throw new InvalidOperationException(
        $"{yourString} is not an underlying value of the YourEnum enumeration."
    );
}

动态（编译时类型未知）：

Type enumType = ...;

// NB: Enums can specify a base type other than 'int'
int numericValue = ...;

object boxedEnumValue = Enum.ToObject(enumType, numericValue);

From an int:

YourEnum foo = (YourEnum)yourInt;

From a string:

YourEnum foo = (YourEnum) Enum.Parse(typeof(YourEnum), yourString);

// The foo.ToString().Contains(",") check is necessary for 
// enumerations marked with a [Flags] attribute.
if (!Enum.IsDefined(typeof(YourEnum), foo) && !foo.ToString().Contains(","))
{
    throw new InvalidOperationException(
        quot;{yourString} is not an underlying value of the YourEnum enumeration."
    );
}

Dynamically (type not known at compile-time):

Type enumType = ...;

// NB: Enums can specify a base type other than 'int'
int numericValue = ...;

object boxedEnumValue = Enum.ToObject(enumType, numericValue);

回复收藏 0 原文

别想她 2024-07-11 14:22:51

来自字符串：（Enum.Parse 已过时，请使用 Enum.TryParse）

enum Importance
{}

Importance importance;

if (Enum.TryParse(value, out importance))
{
}

From a string: (Enum.Parse is out of Date, use Enum.TryParse)

enum Importance
{}

Importance importance;

if (Enum.TryParse(value, out importance))
{
}

回复收藏 0 原文

初见终念 2024-07-11 14:22:51

您应该构建某种类型匹配松弛以使其更加健壮。

public static T ToEnum<T>(dynamic value)
{
    if (value == null)
    {
        // default value of an enum is the object that corresponds to
        // the default value of its underlying type
        // https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/default-values-table
        value = Activator.CreateInstance(Enum.GetUnderlyingType(typeof(T)));
    }
    else if (value is string name)
    {
        return (T)Enum.Parse(typeof(T), name);
    }

    return (T)Enum.ToObject(typeof(T),
             Convert.ChangeType(value, Enum.GetUnderlyingType(typeof(T))));
}

测试用例

[Flags]
public enum A : uint
{
    None  = 0, 
    X     = 1 < 0,
    Y     = 1 < 1
}

static void Main(string[] args)
{
    var value = EnumHelper.ToEnum<A>(7m);
    var x = value.HasFlag(A.X); // true
    var y = value.HasFlag(A.Y); // true

    var value2 = EnumHelper.ToEnum<A>("X");

    var value3 = EnumHelper.ToEnum<A>(null);

    Console.ReadKey();
}

You should build in some type matching relaxation to be more robust.

public static T ToEnum<T>(dynamic value)
{
    if (value == null)
    {
        // default value of an enum is the object that corresponds to
        // the default value of its underlying type
        // https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/default-values-table
        value = Activator.CreateInstance(Enum.GetUnderlyingType(typeof(T)));
    }
    else if (value is string name)
    {
        return (T)Enum.Parse(typeof(T), name);
    }

    return (T)Enum.ToObject(typeof(T),
             Convert.ChangeType(value, Enum.GetUnderlyingType(typeof(T))));
}

Test Case

[Flags]
public enum A : uint
{
    None  = 0, 
    X     = 1 < 0,
    Y     = 1 < 1
}

static void Main(string[] args)
{
    var value = EnumHelper.ToEnum<A>(7m);
    var x = value.HasFlag(A.X); // true
    var y = value.HasFlag(A.Y); // true

    var value2 = EnumHelper.ToEnum<A>("X");

    var value3 = EnumHelper.ToEnum<A>(null);

    Console.ReadKey();
}

回复收藏 0 原文

猫七 2024-07-11 14:22:51

在此处输入图像描述

要将字符串转换为 ENUM 或将 int 转换为 ENUM 常量，我们需要使用 Enum.Parse 函数。这是一个 YouTube 视频https://www.youtube.com/watch?v=4nhx4VwdRDk 它实际上演示了字符串，这同样适用于 int。

代码如下所示，其中“red”是字符串，“MyColors”是具有颜色常量的颜色 ENUM。

MyColors EnumColors = (MyColors)Enum.Parse(typeof(MyColors), "Red");

enter image description here

To convert a string to ENUM or int to ENUM constant we need to use Enum.Parse function. Here is a youtube video https://www.youtube.com/watch?v=4nhx4VwdRDk which actually demonstrate's with string and the same applies for int.

The code goes as shown below where "red" is the string and "MyColors" is the color ENUM which has the color constants.

MyColors EnumColors = (MyColors)Enum.Parse(typeof(MyColors), "Red");

回复收藏 0 原文

岁月蹉跎了容颜 2024-07-11 14:22:51

这是一个标志枚举感知的安全转换方法：

public static bool TryConvertToEnum<T>(this int instance, out T result)
  where T: Enum
{
  var enumType = typeof (T);
  var success = Enum.IsDefined(enumType, instance);
  if (success)
  {
    result = (T)Enum.ToObject(enumType, instance);
  }
  else
  {
    result = default(T);
  }
  return success;
}

This is an flags enumeration aware safe convert method:

public static bool TryConvertToEnum<T>(this int instance, out T result)
  where T: Enum
{
  var enumType = typeof (T);
  var success = Enum.IsDefined(enumType, instance);
  if (success)
  {
    result = (T)Enum.ToObject(enumType, instance);
  }
  else
  {
    result = default(T);
  }
  return success;
}

回复收藏 0 原文

娇女薄笑 2024-07-11 14:22:51

如果您有一个充当位掩码并且可以表示 [Flags] 枚举中的一个或多个值的整数，则可以使用此代码将各个标志值解析到一个列表中：

for (var flagIterator = 0; flagIterator < 32; flagIterator++)
{
    // Determine the bit value (1,2,4,...,Int32.MinValue)
    int bitValue = 1 << flagIterator;

    // Check to see if the current flag exists in the bit mask
    if ((intValue & bitValue) != 0)
    {
        // If the current flag exists in the enumeration, then we can add that value to the list
        // if the enumeration has that flag defined
        if (Enum.IsDefined(typeof(MyEnum), bitValue))
            Console.WriteLine((MyEnum)bitValue);
    }
}

请注意，这假设 < 的基础类型code>enum 是一个有符号的 32 位整数。如果它是不同的数字类型，则必须更改硬编码的 32 以反映该类型中的位（或使用 Enum.GetUnderlyingType() 以编程方式派生它）

If you have an integer that acts as a bitmask and could represent one or more values in a [Flags] enumeration, you can use this code to parse the individual flag values into a list:

for (var flagIterator = 0; flagIterator < 32; flagIterator++)
{
    // Determine the bit value (1,2,4,...,Int32.MinValue)
    int bitValue = 1 << flagIterator;

    // Check to see if the current flag exists in the bit mask
    if ((intValue & bitValue) != 0)
    {
        // If the current flag exists in the enumeration, then we can add that value to the list
        // if the enumeration has that flag defined
        if (Enum.IsDefined(typeof(MyEnum), bitValue))
            Console.WriteLine((MyEnum)bitValue);
    }
}

Note that this assumes that the underlying type of the enum is a signed 32-bit integer. If it were a different numerical type, you'd have to change the hardcoded 32 to reflect the bits in that type (or programatically derive it using Enum.GetUnderlyingType())

回复收藏 0 原文

薄情伤 2024-07-11 14:22:51

有时您有一个 MyEnum 类型的对象。就像

var MyEnumType = typeof(MyEnum);

那时：

Enum.ToObject(typeof(MyEnum), 3)

Sometimes you have an object to the MyEnum type. Like

var MyEnumType = typeof(MyEnum);

Then:

Enum.ToObject(typeof(MyEnum), 3)

回复收藏 0 原文

海未深 2024-07-11 14:22:51

如果您已准备好使用 4.0 .NET 框架，这里有一个新的 Enum.TryParse() 函数非常有用，并且与 [Flags] 属性配合得很好。请参阅Enum.TryParse 方法（字符串，TEnum%）

回复收藏 0 原文

萝莉病 2024-07-11 14:22:51

对于数值，这更安全，因为无论如何它都会返回一个对象：

public static class EnumEx
{
    static public bool TryConvert<T>(int value, out T result)
    {
        result = default(T);
        bool success = Enum.IsDefined(typeof(T), value);
        if (success)
        {
            result = (T)Enum.ToObject(typeof(T), value);
        }
        return success;
    }
}

For numeric values, this is safer as it will return an object no matter what:

public static class EnumEx
{
    static public bool TryConvert<T>(int value, out T result)
    {
        result = default(T);
        bool success = Enum.IsDefined(typeof(T), value);
        if (success)
        {
            result = (T)Enum.ToObject(typeof(T), value);
        }
        return success;
    }
}

回复收藏 0 原文

~没有更多了~

关于作者

暂无简介

0 文章

0 评论

23 人气

关注发私信

相关话题

热门标签

操作系统程序设计 IT运维 Linux系统管理 JavaScript 服务器应用 solaris C/C++ PHP Shell BSD Vue.js aix Oracle Python HTML 系统管理 HTML5 CSS 前端

推荐作者

淡笑忘祈一世凡恋

文章 0 评论 0

我们的影子

文章 0 评论 0

素年丶

文章 0 评论 0

南笙

文章 0 评论 0

18215568913

文章 0 评论 0

qq_xk7Ean

文章 0 评论 0

友情链接

我们使用 Cookies 和其他技术来定制您的体验包括您的登录状态等。通过阅读我们的隐私政策了解更多相关信息。单击 接受 或继续使用网站，即表示您同意使用 Cookies 和您的相关数据。

原文