c# - 你能在运行时添加到枚举类型吗

Question

如果我有枚举类型:

public enum Sport
{
    Tennis = 0;
    Football = 1;
    Squash = 2;
    Volleyball = 3;
}

我可以在运行时以某种方式添加:

PingPong = 4

Answer 1

枚举有一个后备存储，如果不指定则默认为 int。可以直接分配定义值之外的值:

Sport pingPong = (Sport)4;

然后你可以检查它:

if (value == (Sport)4) {}

这就是为什么你有静态函数 Enum.IsDefined()用于检查实际值是否在预期值范围内。请注意，该函数不适用于复合标志值。

bool isValueDefined = Enum.IsDefined(typeof(Sport), value);

编辑:在 Hans Passant 的评论之后:您不必使用文字值 4。您可以使用任何返回 int 的值。例如:

Dictionary<int, string> AdditionalSports = new Dictionary<int, string>();
AdditionalSports.Add(4, "PingPong");

// Usages: if
if (AdditionalSports.ContainsKey(value))
{
    // Maybe do something with AdditionalSports[value], i.e. "PingPong"
}

// In a switch:
switch (value)
{
case default:
    // Since it won't be found in the enum-defined values
    if (AdditionalSports.ContainsKey(value))
    {
        // Maybe do something with AdditionalSports[value], i.e. "PingPong"
    }
}