位标志 - 我错过了什么？

Question

一个简单的代码：

protected void Page_Load(object sender, EventArgs e)
{
    DateTime now = DateTime.UtcNow;

    lit.Text += "<br/>now.DayOfWeek: " + now.DayOfWeek.ToString();

    // weekdays (Saturday is not included)
    DayOfWeek runningDays = DayOfWeek.Monday | DayOfWeek.Tuesday | DayOfWeek.Wednesday | DayOfWeek.Thursday | DayOfWeek.Friday;

    lit.Text += "<br/>" + runningDays.HasFlag(now.DayOfWeek);
    lit.Text += "<br/>" + runningDays.HasAny(now.DayOfWeek);
    lit.Text += "<br/>" + ((runningDays & now.DayOfWeek) != 0);

    // weekend (Saturday is in a weekend)
    runningDays = DayOfWeek.Saturday | DayOfWeek.Sunday;

    lit.Text += "<br/>" + runningDays.HasFlag(now.DayOfWeek);
    lit.Text += "<br/>" + runningDays.HasAny(now.DayOfWeek);
    lit.Text += "<br/>" + ((runningDays & now.DayOfWeek) != 0);
}

助手：

public static bool HasExactly(this DayOfWeek x, DayOfWeek y) { return x == y; }
public static bool HasAny(this DayOfWeek x, DayOfWeek y) { return 0 != (x & y); }
public static bool HasAll(this DayOfWeek x, DayOfWeek y) { return y == (x & y); }

今天的输出（星期六）

now.DayOfWeek: Saturday
True
True
True
True
True
True 

但输出应该是这样的：

now.DayOfWeek: Saturday
False
False
False
True
True
True 

我在这里缺少什么？

Answer 1

星期几不是位标志。 http://msdn.microsoft.com/en-us/library /system.datetime.dayofweek.aspx

中常量的值
DayOfWeek 枚举范围为
DayOfWeek.Sunday 至
DayOfWeek.Saturday。如果投射到
整数，其值范围从零开始
（表示 DayOfWeek.Sunday）
六（这表明
DayOfWeek.Saturday)。

Answer 2

我知道这是一篇旧文章，但以防万一 - 进行标志枚举的简洁语法是

[Flags]
public enum DaysOfWeek
{
    None = 1 << 0,
    Monday = 1 << 1,
    Tuesday = 1 << 2,
    Wednesday = 1 << 3,
    Thursday = 1 << 4,
    Friday = 1 << 5,
    Saturday = 1 << 6,
    Sunday = 1 << 7
}

您需要 None 来指示没有选择任何内容。这样的枚举允许您指示多天，例如：

var selectedDays = DaysOfWeek.Tuesday | DaysOfWeek.Friday;

希望不需要注释。为了“解码”该值：

public bool IsDayOfWeekSelected(DaysOfWeek which, DaysOfWeek selection)
{
    return selection & which == which;
}

然后这允许我们调用：

var isTuesday = IsDayOfWeekSelected(DaysOfWeek.Tuesday, selectedDays); // => true
var isWednesday = IsDayOfWeekSelected(DaysOfWeek.Wednesday, selectedDays); // => false
var isFriday = IsDayOfWeekSelected(DaysOfWeek.Friday, selectedDays); // => true

希望这对某人有帮助。

Answer 3

如果您需要像标志一样使用它，您可以创建自己的 DayOfWeek 枚举：

[Flags]
public enum MyDayOfWeek { Sunday = 1, Monday = 2, Tuesday = 4, ... , Saturday = 64 };

Answer 4

DayOfWeek 有连续的数字。

使用List。

转到定义显示：

// Summary:
//     Specifies the day of the week.
[Serializable]
[ComVisible(true)]
public enum DayOfWeek
{
    // Summary:
    //     Indicates Sunday.
    Sunday = 0,
    //
    // Summary:
    //     Indicates Monday.
    Monday = 1,
    //
    // Summary:
    //     Indicates Tuesday.
    Tuesday = 2,
    //
    // Summary:
    //     Indicates Wednesday.
    Wednesday = 3,
    //
    // Summary:
    //     Indicates Thursday.
    Thursday = 4,
    //
    // Summary:
    //     Indicates Friday.
    Friday = 5,
    //
    // Summary:
    //     Indicates Saturday.
    Saturday = 6,
}

Answer 5

DayOfWeek 枚举旨在表示一周中的某一天，而不是一组天。

使用 & 不会出现编译器错误，因为枚举是整数，但运算符不会执行您期望的操作（除非您恰好只在星期一、星期二或星期四安排事件） 。

如果你想要一个位标志，那么声明一个位标志类型，就像 Ray 建议的那样。