类似于Cast int to enum in C#,但我的枚举是一个泛型类型参数。处理这个问题的最好方法是什么?
示例:
private T ConvertEnum<T>(int i) where T : struct, IConvertible
{
return (T)i;
}
生成编译器错误Cannot convert type 'int' to 'T'
完整代码如下所示,value可以包含int,也可以包含null。
private int? TryParseInt(string value)
{
var i = 0;
if (!int.TryParse(value, out i))
{
return null;
}
return i;
}
private T? TryParseEnum<T>(string value) where T : struct, IConvertible
{
var i = TryParseInt(value);
if (!i.HasValue)
{
return null;
}
return (T)i.Value;
}
发布于 2012-05-01 00:30:18
我发现的最简单的方法是通过向object
添加强制转换来强制编译器。
return (T)(object)i.Value;
发布于 2014-10-10 08:02:42
这里有一个非常快速的解决方案,它滥用了运行库创建静态泛型类的多个实例这一事实。释放你内心的优化心魔吧!
当你以一种通用的方式从一个流中读取枚举时,这真的很有用。结合外部类(也缓存枚举的底层类型)和BitConverter来释放令人敬畏的。
void Main()
{
Console.WriteLine("Cast (reference): {0}", (TestEnum)5);
Console.WriteLine("EnumConverter: {0}", EnumConverter<TestEnum>.Convert(5));
Console.WriteLine("Enum.ToObject: {0}", Enum.ToObject(typeof(TestEnum), 5));
int iterations = 1000 * 1000 * 100;
Measure(iterations, "Cast (reference)", () => { var t = (TestEnum)5; });
Measure(iterations, "EnumConverter", () => EnumConverter<TestEnum>.Convert(5));
Measure(iterations, "Enum.ToObject", () => Enum.ToObject(typeof(TestEnum), 5));
}
static class EnumConverter<TEnum> where TEnum : struct, IConvertible
{
public static readonly Func<long, TEnum> Convert = GenerateConverter();
static Func<long, TEnum> GenerateConverter()
{
var parameter = Expression.Parameter(typeof(long));
var dynamicMethod = Expression.Lambda<Func<long, TEnum>>(
Expression.Convert(parameter, typeof(TEnum)),
parameter);
return dynamicMethod.Compile();
}
}
enum TestEnum
{
Value = 5
}
static void Measure(int repetitions, string what, Action action)
{
action();
var total = Stopwatch.StartNew();
for (int i = 0; i < repetitions; i++)
{
action();
}
Console.WriteLine("{0}: {1}", what, total.Elapsed);
}
启用优化的酷睿i7-3740QM上的结果:
Cast (reference): Value
EnumConverter: Value
Enum.ToObject: Value
Cast (reference): 00:00:00.3175615
EnumConverter: 00:00:00.4335949
Enum.ToObject: 00:00:14.3396366
发布于 2018-06-21 16:22:14
或者,如果您不能将枚举作为泛型类型获取,而是作为type获取,则只需使用
Enum.ToObject
https://msdn.microsoft.com/en-us/library/system.enum.toobject(v=vs.110).aspx
https://stackoverflow.com/questions/10387095
复制相似问题