我从根本上误解了HasFlags的工作原理吗?我不明白为什么这段代码失败了。为什么我的[Flag]枚举验证失败?
此代码取值并确定它是否是我的枚举值的有效组合。
Enum值的两个子组由ORing其他成员标识:JustTheMonths和Exclusives。 JustTheMonths是在Enum中声明的,而Exclusives是在验证方法中构建的。
当我将1或2(未分配或未知)传递给此方法时,它将它们正确地标识为有效 - 独占,但不是JustTheMonths的成员。
但是,当我将4传递给此代码时,它正确地将其识别为整个集合的成员,但将其错误地标识为子集合JustTheMonths的成员。
我在这里做错了什么?为什么我的代码认为4是(8 | 16 | 32 | 64 | 128 | 256 | 512 | 1024 | 2048 | 4096 | 8172 | 16344)的成员?
private void Form1_Load(object sender, EventArgs e)
{
FloweringMonth test = FloweringMonth.NotApplicable;
if (IsValidFloweringMonthValue((int)test))
{
System.Diagnostics.Debug.WriteLine("Valid");
}
else
{
System.Diagnostics.Debug.WriteLine("Not Valid");
}
}
[Flags]
public enum FloweringMonth
{
Unassigned = 1, Unknown = 2, NotApplicable = 4,
Jan = 8, Feb = 16, Mar = 32, Apr = 64, May = 128, Jun = 256,
Jul = 512, Aug = 1024, Sep = 2048, Oct = 4086, Nov = 8172, Dec = 16344,
JustMonths = (Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec)
}
public static bool IsValidFloweringMonthValue(int value)
{
FloweringMonth incoming = (FloweringMonth)value;
FloweringMonth AllVals = FloweringMonth.Unassigned | FloweringMonth.Unknown |
FloweringMonth.NotApplicable | FloweringMonth.Jan | FloweringMonth.Feb |
FloweringMonth.Mar | FloweringMonth.Apr | FloweringMonth.May |
FloweringMonth.Jun | FloweringMonth.Jul | FloweringMonth.Aug |
FloweringMonth.Sep | FloweringMonth.Oct | FloweringMonth.Nov | FloweringMonth.Dec;
// does the incoming value contain any enum values from AllVals?
bool HasMembersOfAll = AllVals.HasFlag(incoming);
if (!HasMembersOfAll) return false;
// does the incoming value contain any enum values from JustTheMonths?
bool HasMembersOfMonths = FloweringMonth.JustMonths.HasFlag(incoming);
// does it contain any enum values from the set of three exclusive values?
FloweringMonth Exclusives = (FloweringMonth.Unassigned |
FloweringMonth.Unknown | FloweringMonth.NotApplicable);
bool HasMembersOfExclusives = Exclusives.HasFlag(incoming);
// an exclusive value cannot be mixed with any month values
if (HasMembersOfMonths && HasMembersOfExclusives) return false; // bad combo
// an exclusive value cannot be mixed with other exclusive values
if (incoming.HasFlag(FloweringMonth.Unassigned) &&
incoming.HasFlag(FloweringMonth.Unknown)) return false;
if (incoming.HasFlag(FloweringMonth.Unassigned) &&
incoming.HasFlag(FloweringMonth.NotApplicable)) return false;
if (incoming.HasFlag(FloweringMonth.Unknown) &&
incoming.HasFlag(FloweringMonth.NotApplicable)) return false;
return true;
}
从https://msdn.microsoft.com/en-us/library/system.enum(v=vs.110).aspx: 。 。定义两个幂的枚举常量,即1,2,4,8等等。这意味着组合枚举常量中的各个标志不会重叠。 –
@ m-y嗯,没有。编译器在没有显式值的情况下分配'0,1,2,3,4,...'。 Flags属性不会改变这种行为。 –
@KennethK .:我纠正了,你是对的。 –