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我是否从根本上误解了 HasFlags 的工作原理？我不明白为什么这段代码会失败。

此代码采用一个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 在 Enum 中声明，Exclusives 在验证方法中内置。

当我将 1 或 2（未分配或未知）传递给此方法时，它会正确地将它们标识为有效 - 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，但错误地将其识别为子组 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;
    }
4

2 回答 2

4

在@dukedukes 回答之后，问题在于您的 2 的倍数已关闭。

避免此错误的一种方法是使用bitwise右侧的操作。

[Flags]
enum Months
{
    January = 1 << 3, // 8
    February = 1 << 4, // 16
    March = 1 << 5, // 32
}
于 2016-09-27T01:02:03.593 回答
2

您的 2 的倍数不正确。4086应该是4096，8172应该是8192，等等……

于 2016-09-27T00:52:10.630 回答