如何定义多个值映射到单个标签的枚举？

Question

假设,为了这个例子,我试图解析一个文件,该文件指定记录中的两个任意字节代表星期几,因此:

DayOfWeek:

 - 0    = Monday
 - 1    = Tuesday
 - 2    = Wednesday
 - 3    = Thursday
 - 4    = Friday
 - 5    = Saturday
 - 6    = Sunday
 - 7-15 = Reserved for Future Use

我可以定义一个枚举来映射到这个字段,因此:

public enum DaysOfWeek
{
     Monday = 0,
     Tuesday = 1,
     Wednesday = 2,
     Thursday = 3,
     Friday = 4,
     Saturday = 5,
     Sunday = 6
     ReservedForFutureUse
}

但是如何定义有效值ReservedForFutureUse呢？理想情况下,我想做的事情如下:

public enum DaysOfWeek
    {
         Monday = 0,
         Tuesday = 1,
         Wednesday = 2,
         Thursday = 3,
         Friday = 4,
         Saturday = 5,
         Sunday = 6
         ReservedForFutureUse = {7,8,9,10,11,12,13,14,15}
    }

只有更复杂的领域才会加剧这个问题; 例如,假设在这种情况下,7和8都映射到相同的错误情况或其他内容.如何在C#枚举中捕获此要求？

Answer 1

枚举的一个有趣的怪癖是，定义为某种枚举类型的变量可以保存未由该枚举的任何成员定义的值：

public enum DaysOfWeek
{
     Monday = 0,
     Tuesday = 1,
     Wednesday = 2,
     Thursday = 3,
     Friday = 4,
     Saturday = 5,
     Sunday = 6
}

// in other code
DaysOfWeek someDay = (DaysOfWeek)42; // this is perfectly legal

这意味着您实际上并不需要定义所有可能出现的值，而只需指定那些对您的代码有意义的值即可。然后你可以使用一些“catch-all” if- 或switch- 块来处理未定义的值：

switch (someDay)
{
    case DaysOfWeek.Monday:
    {
        // do monday stuff
        break;
    }
    case DaysOfWeek.Tuesday:
    {
        // do tuesday stuff
        break;
    }
    // [...] handle the other weekdays [...]
    default:
    {
        // handle undefined values here
        break;
    }
}

Answer 2

尽管给定的基础值可以映射到多个enum值，但一个enum值可以只具有一个基础值。

你可以这样做

public enum DaysOfWeek
{
     Monday = 0,
     Tuesday = 1,
     Wednesday = 2,
     Thursday = 3,
     Friday = 4,
     Saturday = 5,
     Sunday = 6
     Reserved1 = 7
     ...
     Reserved8 = 15
}