从C#中的枚举中获取int值

Question

我有一个叫Questions(复数)的类.在这个类中有一个名为Question(单数)的枚举,看起来像这样.

public enum Question
{
    Role = 2,
    ProjectFunding = 3,
    TotalEmployee = 4,
    NumberOfServers = 5,
    TopBusinessConcern = 6
}

在Questions类中,我有一个get(int foo)函数返回一个Questions对象foo.有没有一种简单的方法从枚举中获取整数值,所以我可以做类似的事情Questions.Get(Question.Role)？

Answer 1

刚刚施放枚举,例如

int something = (int) Question.Role;

以上内容适用于您在野外看到的绝大多数枚举,因为枚举的默认基础类型是int.

但是,正如cecilphillip指出的那样,枚举可以有不同的底层类型.如果枚举被声明为uint,long,或ulong,应当投射到枚举的类型; 例如

enum StarsInMilkyWay:long {Sun = 1, V645Centauri = 2 .. Wolf424B = 2147483649};

你应该使用

long something = (long)StarsInMilkyWay.Wolf424B;

Answer 2

由于枚举可以是任何整数类型(byte,int,short等),更鲁棒的方式来获得的枚举的基本积分值将是使使用的GetTypeCode方法与结合Convert类:

enum Sides {
    Left, Right, Top, Bottom
}
Sides side = Sides.Bottom;

object val = Convert.ChangeType(side, side.GetTypeCode());
Console.WriteLine(val);

无论底层整数类型如何,这都应该有效.

Answer 3

将其声明为具有公共常量的静态类:

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

然后你可以引用它Question.Role,并且它总是评估为int或者你定义它的任何东西.

Answer 4

Question question = Question.Role;
int value = (int) question;

会导致value == 2.

Answer 5

在相关的说明中,如果您想从中获取int值System.Enum,则e在此处给出:

Enum e = Question.Role;

您可以使用:

int i = Convert.ToInt32(e);
int i = (int)(object)e;
int i = (int)Enum.Parse(e.GetType(), e.ToString());
int i = (int)Enum.ToObject(e.GetType(), e);

最后两个是丑陋的.我更喜欢第一个.

Answer 6

它比你想象的容易 - 枚举已经是一个整数.它只需要提醒:

int y = (int)Question.Role;
Console.WriteLine(y); // prints 2

Answer 7

例:

public Enum EmpNo
{
    Raj = 1,
    Rahul,
    Priyanka
}

并在后面的代码中获取枚举值:

int setempNo = (int)EmpNo.Raj; //This will give setempNo = 1

要么

int setempNo = (int)EmpNo.Rahul; //This will give setempNo = 2

枚举将增加1,您可以设置起始值.如果未设置起始值,则最初将其指定为0.

Answer 8

我最近在代码中转而使用枚举,转而使用带有受保护构造函数和预定义静态实例的类(感谢Roelof - C# Ensure Valid Enum Values - Futureproof Method).

鉴于此,下面是我现在如何解决这个问题(包括隐式转换为/来自int).

public class Question
{
    // Attributes
    protected int index;
    protected string name;
    // Go with a dictionary to enforce unique index
    //protected static readonly ICollection<Question> values = new Collection<Question>();
    protected static readonly IDictionary<int,Question> values = new Dictionary<int,Question>();

    // Define the "enum" values
    public static readonly Question Role = new Question(2,"Role");
    public static readonly Question ProjectFunding = new Question(3, "Project Funding");
    public static readonly Question TotalEmployee = new Question(4, "Total Employee");
    public static readonly Question NumberOfServers = new Question(5, "Number of Servers");
    public static readonly Question TopBusinessConcern = new Question(6, "Top Business Concern");

    // Constructors
    protected Question(int index, string name)
    {
        this.index = index;
        this.name = name;
        values.Add(index, this);
    }

    // Easy int conversion
    public static implicit operator int(Question question) =>
        question.index; //nb: if question is null this will return a null pointer exception

    public static implicit operator Question(int index) =>        
        values.TryGetValue(index, out var question) ? question : null;

    // Easy string conversion (also update ToString for the same effect)
    public override string ToString() =>
        this.name;

    public static implicit operator string(Question question) =>
        question?.ToString();

    public static implicit operator Question(string name) =>
        name == null ? null : values.Values.FirstOrDefault(item => name.Equals(item.name, StringComparison.CurrentCultureIgnoreCase));


    // If you specifically want a Get(int x) function (though not required given the implicit converstion)
    public Question Get(int foo) =>
        foo; //(implicit conversion will take care of the conversion for you)
}

这种方法的优点是你可以从枚举中获得所有内容,但是你的代码现在更加灵活,所以如果你需要根据值执行不同的操作Question,你可以将逻辑放入Question自身(即在首选的OO中)时尚)而不是在整个代码中放置大量的case语句来处理每个场景.

注意:答案更新2018-04-27以利用C#6功能; 即声明表达式和lambda表达式主体定义.查看原始代码的修订历史记录.这样做的好处是使定义不那么冗长; 这是对这个答案方法的主要抱怨之一.

Answer 9

如果你想得到一个存储在一个变量中的枚举值的整数,那个类型就是Question,例如在一个方法中使用,你可以简单地这样做我在这个例子中写的:

enum Talen
{
    Engels = 1, Italiaans = 2, Portugees = 3, Nederlands = 4, Duits = 5, Dens = 6
}

Talen Geselecteerd;    

public void Form1()
{
    InitializeComponent()
    Geselecteerd = Talen.Nederlands;
}

// You can use the Enum type as a parameter, so any enumeration from any enumerator can be used as parameter
void VeranderenTitel(Enum e)
{
    this.Text = Convert.ToInt32(e).ToString();
}

这会将窗口标题更改为4,因为变量Geselecteerd是Talen.Nederlands.如果我将其更改为Talen.Portugees并再次调用该方法,则文本将更改为3.

我很难在互联网上找到这个简单的解决方案而我找不到它,所以我正在测试一些东西并发现了这一点.希望这可以帮助.;)

Answer 10

要确保存在枚举值然后解析它,您还可以执行以下操作.

// Fake Day of Week
string strDOWFake = "SuperDay";
// Real Day of Week
string strDOWReal = "Friday";
// Will hold which ever is the real DOW.
DayOfWeek enmDOW;

// See if fake DOW is defined in the DayOfWeek enumeration.
if (Enum.IsDefined(typeof(DayOfWeek), strDOWFake))
{
// This will never be reached since "SuperDay" 
// doesn't exist in the DayOfWeek enumeration.
    enmDOW = (DayOfWeek)Enum.Parse(typeof(DayOfWeek), strDOWFake);
}
// See if real DOW is defined in the DayOfWeek enumeration.
else if (Enum.IsDefined(typeof(DayOfWeek), strDOWReal))
{
    // This will parse the string into it's corresponding DOW enum object.
    enmDOW = (DayOfWeek)Enum.Parse(typeof(DayOfWeek), strDOWReal);
}

// Can now use the DOW enum object.
Console.Write("Today is " + enmDOW.ToString() + ".");

我希望这有帮助.

Answer 11

也许我错过了它,但有人试过一个简单的通用扩展方法.这对我很有用.您可以通过这种方式避免API中的类型转换,但最终会导致更改类型操作.这是编程Roselyn以使编译器为您创建GetValue方法的好例子.

    public static void Main()
    {
        int test = MyCSharpWrapperMethod(TestEnum.Test1);

        Debug.Assert(test == 1);
    }

    public static int MyCSharpWrapperMethod(TestEnum customFlag)
    {
        return MyCPlusPlusMethod(customFlag.GetValue<int>());
    }

    public static int MyCPlusPlusMethod(int customFlag)
    {
        //Pretend you made a PInvoke or COM+ call to C++ method that require an integer
        return customFlag;
    }

    public enum TestEnum
    {
        Test1 = 1,
        Test2 = 2,
        Test3 = 3
    }
}

public static class EnumExtensions
{
    public static T GetValue<T>(this Enum enumeration)
    {
        T result = default(T);

        try
        {
            result = (T)Convert.ChangeType(enumeration, typeof(T));
        }
        catch (Exception ex)
        {
            Debug.Assert(false);
            Debug.WriteLine(ex);
        }

        return result;
    }
}    

Answer 12

还有一种方法:

Console.WriteLine("Name: {0}, Value: {0:D}", Question.Role);

将导致:

Name: Role, Value: 2

Answer 13

public enum QuestionType
{
    Role = 2,
    ProjectFunding = 3,
    TotalEmployee = 4,
    NumberOfServers = 5,
    TopBusinessConcern = 6
}

......是一个很好的宣言.

你必须像这样将结果转换为int:

int Question = (int)QuestionType.Role

否则,类型仍然是QuestionType.

这种严格程度是C#方式.

另一种方法是使用类声明:

public class QuestionType
{
    public static int Role = 2,
    public static int ProjectFunding = 3,
    public static int TotalEmployee = 4,
    public static int NumberOfServers = 5,
    public static int TopBusinessConcern = 6
}

声明它不太优雅,但你不需要在代码中强制转换它:

int Question = QuestionType.Role

或者,您可能会对使用Visual Basic感到更舒服,因为Visual Basic可以满足许多领域的这种期望.

Answer 14

您可以通过对定义的枚举类型实现扩展方法来执行此操作:

public static class MyExtensions
{
    public static int getNumberValue(this Question questionThis)
    {
        return (int)questionThis;
    }
}

这简化了获取当前枚举值的int值:

Question question = Question.Role;
int value = question.getNumberValue();

要么

int value = Question.Role.getNumberValue();

Answer 15

int number = Question.Role.GetHashCode();

number应该有价值2.

Answer 16

用：

Question question = Question.Role;
int value = question.GetHashCode();

它会导致value == 2.

仅当枚举适合int.

Answer 17

如何改为扩展方法:

public static class ExtensionMethods
{
    public static int IntValue(this Enum argEnum)
    {
        return Convert.ToInt32(argEnum);
    }
}

而且用法稍微漂亮一些:

var intValue = Question.Role.IntValue();

Answer 18

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

Console.WriteLine((int)(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));

if (typeof(Suit).IsEnumDefined("Spades"))
{
    var res = (int)(Suit)Enum.Parse(typeof(Suit), "Spades");
    Console.Out.WriteLine("{0}", res);
}

Answer 19

我最喜欢的 int 或更小的枚举 hack：

GetHashCode();

对于一个枚举

public enum Test
{
    Min = Int32.MinValue,
    One = 1,
    Max = Int32.MaxValue,
}

这，

var values = Enum.GetValues(typeof(Test));

foreach (var val in values)
{
    Console.WriteLine(val.GetHashCode());
    Console.WriteLine(((int)val));
    Console.WriteLine(val);
}

输出

one
1
1
max
2147483647
2147483647
min
-2147483648
-2147483648

免责声明：

它不适用于基于 long 的枚举。

Answer 20

您应该使用类型转换，就像我们可以在任何其他语言中使用一样。

如果你enum是这样的——

public enum Question
{
    Role = 2,
    ProjectFunding = 3,
    TotalEmployee = 4,
    NumberOfServers = 5,
    TopBusinessConcern = 6
}

你需要转换为int，然后执行此操作 -

Question q = Question.Role;
.............
.............
int something = (int) q;

关于-

在 C# 中，有两种类型的转换：

• 隐式转换（自动） - 将较小的类型转换为较大的类型大小，例如 -

char-> int-> long-> float->double

• 显式转换（手动） - 将较大的类型转换为较小的类型，例如 -

double-> float-> long-> int->char

更多内容可以在这里找到。

Answer 21

我能想到的最简单的解决方案是重载该Get(int)方法，如下所示：

[modifiers] Questions Get(Question q)
{
    return Get((int)q);
}

其中[modifiers]通常可以与方法相同Get(int)。如果您无法编辑该类Questions或由于某种原因不想编辑该类，您可以通过编写扩展来重载该方法：

public static class Extensions
{
    public static Questions Get(this Questions qs, Question q)
    {
        return qs.Get((int)q);
    }
}

Answer 22

我想建议“从枚举中获取‘int’值”的例子是

public enum Sample
{
    Book = 1, 
    Pen = 2, 
    Pencil = 3
}

int answer = (int)Sample.Book;

现在答案是1。

Answer 23

由于可以用多种基本类型声明枚举，所以泛型转换任何枚举类型的通用扩展方法可能会很有用。

enum Box
{
    HEIGHT,
    WIDTH,
    DEPTH
}

public static void UseEnum()
{
    int height = Box.HEIGHT.GetEnumValue<int>();
    int width = Box.WIDTH.GetEnumValue<int>();
    int depth = Box.DEPTH.GetEnumValue<int>();
}

public static T GetEnumValue<T>(this object e) => (T)e;