如何检查是否设置了标志组合的标志？
如何检查是否设置了标志组合的标志？
提问于 2009-08-27 09:44:00
假设我有这个枚举：
[Flags]
enum Letters
{
A = 1,
B = 2,
C = 4,
AB = A | B,
All = A | B | C,
}例如，要检查是否设置了AB，我可以这样做：
if((letter & Letters.AB) == Letters.AB)有没有比下面更简单的方法来检查组合标志常量的任何标志是否被设置？
if((letter & Letters.A) == Letters.A || (letter & Letters.B) == Letters.B)例如，可以将&换成其他东西吗？
回答 13
Stack Overflow用户
发布于 2012-03-20 12:10:20
在.NET 4中，您可以使用Enum.HasFlag method：
using System;
[Flags] public enum Pet {
None = 0,
Dog = 1,
Cat = 2,
Bird = 4,
Rabbit = 8,
Other = 16
}
public class Example
{
public static void Main()
{
// Define three families: one without pets, one with dog + cat and one with a dog only
Pet[] petsInFamilies = { Pet.None, Pet.Dog | Pet.Cat, Pet.Dog };
int familiesWithoutPets = 0;
int familiesWithDog = 0;
foreach (Pet petsInFamily in petsInFamilies)
{
// Count families that have no pets.
if (petsInFamily.Equals(Pet.None))
familiesWithoutPets++;
// Of families with pets, count families that have a dog.
else if (petsInFamily.HasFlag(Pet.Dog))
familiesWithDog++;
}
Console.WriteLine("{0} of {1} families in the sample have no pets.",
familiesWithoutPets, petsInFamilies.Length);
Console.WriteLine("{0} of {1} families in the sample have a dog.",
familiesWithDog, petsInFamilies.Length);
}
}该示例显示以下输出：
// 1 of 3 families in the sample have no pets.
// 2 of 3 families in the sample have a dog.Stack Overflow用户
发布于 2009-08-27 10:08:54
我使用扩展方法来编写类似这样的东西：
if (letter.IsFlagSet(Letter.AB))
...代码如下：
public static class EnumExtensions
{
private static void CheckIsEnum<T>(bool withFlags)
{
if (!typeof(T).IsEnum)
throw new ArgumentException(string.Format("Type '{0}' is not an enum", typeof(T).FullName));
if (withFlags && !Attribute.IsDefined(typeof(T), typeof(FlagsAttribute)))
throw new ArgumentException(string.Format("Type '{0}' doesn't have the 'Flags' attribute", typeof(T).FullName));
}
public static bool IsFlagSet<T>(this T value, T flag) where T : struct
{
CheckIsEnum<T>(true);
long lValue = Convert.ToInt64(value);
long lFlag = Convert.ToInt64(flag);
return (lValue & lFlag) != 0;
}
public static IEnumerable<T> GetFlags<T>(this T value) where T : struct
{
CheckIsEnum<T>(true);
foreach (T flag in Enum.GetValues(typeof(T)).Cast<T>())
{
if (value.IsFlagSet(flag))
yield return flag;
}
}
public static T SetFlags<T>(this T value, T flags, bool on) where T : struct
{
CheckIsEnum<T>(true);
long lValue = Convert.ToInt64(value);
long lFlag = Convert.ToInt64(flags);
if (on)
{
lValue |= lFlag;
}
else
{
lValue &= (~lFlag);
}
return (T)Enum.ToObject(typeof(T), lValue);
}
public static T SetFlags<T>(this T value, T flags) where T : struct
{
return value.SetFlags(flags, true);
}
public static T ClearFlags<T>(this T value, T flags) where T : struct
{
return value.SetFlags(flags, false);
}
public static T CombineFlags<T>(this IEnumerable<T> flags) where T : struct
{
CheckIsEnum<T>(true);
long lValue = 0;
foreach (T flag in flags)
{
long lFlag = Convert.ToInt64(flag);
lValue |= lFlag;
}
return (T)Enum.ToObject(typeof(T), lValue);
}
public static string GetDescription<T>(this T value) where T : struct
{
CheckIsEnum<T>(false);
string name = Enum.GetName(typeof(T), value);
if (name != null)
{
FieldInfo field = typeof(T).GetField(name);
if (field != null)
{
DescriptionAttribute attr = Attribute.GetCustomAttribute(field, typeof(DescriptionAttribute)) as DescriptionAttribute;
if (attr != null)
{
return attr.Description;
}
}
}
return null;
}
}Stack Overflow用户
发布于 2013-06-24 18:54:24
在.NET 4或更高版本中有HasFlag方法。
if(letter.HasFlag(Letters.AB))
{
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/1339976
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