C#enum type-safety

有没有办法强制C#枚举只接受几个明确命名的常量之一,还是有另一个功能呢？ C#参考有了这个想法：

It is possible to assign any arbitrary integer value to an enum type.
However, you should not do this because the implicit expectation is
that an enum variable will only hold one of the values defined by the
enum. To assign an arbitrary value to a variable of an enumeration
type is to introduce a high risk for errors.

(一种新的语言设计允许这种邋..这让我感到困惑.)

解决方法:

据我所知,你不能阻止C#允许枚举和整数之间的转换.

作为一种变通方法,您可以使用具有受限实例化的自定义类型.用法看起来类似,但您也可以为此类型定义方法和运算符.

说你有这个枚举：

enum DayOfWeek
{
    Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday 
}

您可以在其位置使用密封类.优点是您可以免费进行比较(因为在这种情况下,值比较和参考比较是等效的).缺点是(像C#中的所有引用类型一样),它可以为空.

sealed class DayOfWeek
{
    public static readonly DayOfWeek Monday = new DayOfWeek(0);
    public static readonly DayOfWeek Tuesday = new DayOfWeek(1);
    public static readonly DayOfWeek Wednesday = new DayOfWeek(2);
    public static readonly DayOfWeek Thursday = new DayOfWeek(3);
    public static readonly DayOfWeek Friday = new DayOfWeek(4);
    public static readonly DayOfWeek Saturday = new DayOfWeek(5);
    public static readonly DayOfWeek Sunday = new DayOfWeek(6);

    private readonly int _value;

    private DayOfWeek(int value) 
    {
        _value = value;
    }
}

或者您可以使用结构.它的优点是它不可空,因此它更类似于枚举.缺点是你必须手动实现比较代码：

struct DayOfWeek
{
    public static readonly DayOfWeek Monday = new DayOfWeek(0);
    public static readonly DayOfWeek Tuesday = new DayOfWeek(1);
    public static readonly DayOfWeek Wednesday = new DayOfWeek(2);
    public static readonly DayOfWeek Thursday = new DayOfWeek(3);
    public static readonly DayOfWeek Friday = new DayOfWeek(4);
    public static readonly DayOfWeek Saturday = new DayOfWeek(5);
    public static readonly DayOfWeek Sunday = new DayOfWeek(6);

    private readonly int _value;

    private DayOfWeek(int value)
    {
        _value = value;
    }

    public bool Equals(DayOfWeek other)
    {
        return _value == other._value;
    }

    public override bool Equals(object obj)
    {
        if (ReferenceEquals(null, obj))
        {
            return false;
        }
        return obj is DayOfWeek && Equals((DayOfWeek)obj);
    }

    public override int GetHashCode()
    {
        return _value;
    }

    public static bool operator ==(DayOfWeek op1, DayOfWeek op2)
    {
        return op1.Equals(op2);
    }

    public static bool operator !=(DayOfWeek op1, DayOfWeek op2)
    {
        return !(op1 == op2);
    }
}

标签：c,enums,type-safety
来源： https://codeday.me/bug/20190609/1203315.html