c#枚举索引问题
本文关键字:问题 索引 枚举 | 更新日期: 2023-09-27 18:09:04
是否可以使用索引整数来获取enum
值?例如,if…
public enum Days { Mon, Tues, Wed, ..., Sun};
…有没有可能写一些像……
Days currentDay = Days[index];
谢谢!
不,但是您可以将int
转换为enum
,如果您正在使用的值在enum
中定义,但是您这样做需要自行承担风险:
Days currentDay = (Days)index;
如果你真的想要安全,你可以先检查它是否被定义,但这会涉及到一些装箱等问题,并会影响性能。
// checks to see if a const exists with the given value.
if (Enum.IsDefined(typeof(Days), index))
{
currentDay = (Days)index;
}
如果你知道你的enum是一个指定的,连续的值范围(即Mon = 0到Sun = 6),你可以比较:
if (index >= (int)Days.Mon && index <= (int)Days.Sun)
{
currentDay = (Days) index;
}
您也可以使用由Enum.GetValues()
传递回来的数组,但这再次比强制转换要重:
Day = (Day)Enum.GetValues(typeof(Day))[index];
如果对枚举进行了正确的索引,则可以将int(或其他索引)归为枚举。
所以…
public enum Days { Mon = 0, Tue, Wed .... }
Days today = (Days)1;
我必须做一些计算与DaysOfWeek
enum之前。我使用一个扩展方法来创建一个安全的默认值。
下面是一个例子:
public enum Days { Invalid = ~0, Mon, Tues, Wed, Thurs, Fri, Sat, Sun };
class Program
{
static void Main(string[] args)
{
int day = 8;
Days day8 = (Days)day;
Console.WriteLine("The eighth day is {0}", day8);
Console.WriteLine("Days contains {0}: {1}",
day, Enum.IsDefined(typeof(Days), day));
Console.WriteLine("Invalid day if {0} doesn't exist: {1}",
day, day8.OrDefault(Days.Invalid) );
Console.WriteLine("Sunday day if {0} doesn't exist: {1}",
day, day8.OrDefault(Days.Sun));
Days day9 = ((Days)9).OrDefault(Days.Wed);
Console.WriteLine("Day (9) defaulted: {1}", 9, day9);
Console.ReadLine();
}
}
public static class DaysExtensions
{
public static Days OrDefault(this Days d, Days defaultDay)
{
if (Enum.IsDefined(typeof(Days), (Days)d))
{
return d;
}
return defaultDay;
}
}
输出:
The eighth day is 8
Days contains 8: False
Invalid day if 8 doesn't exist: Invalid
Sunday day if 8 doesn't exist: Sun
Day (9) defaulted: Wed