Bit Flags - What am I missing?

Question

a simple code:

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);
}

A helper:

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); }

today's output (Saturday)

now.DayOfWeek: Saturday
True
True
True
True
True
True 

But the output should be like:

now.DayOfWeek: Saturday
False
False
False
True
True
True 

What am I missing here?

Answer 1

Days of week are not bit flags. http://msdn.microsoft.com/en-us/library/system.datetime.dayofweek.aspx

The value of the constants in the DayOfWeek enumeration ranges from DayOfWeek.Sunday to DayOfWeek.Saturday. If cast to an integer, its value ranges from zero (which indicates DayOfWeek.Sunday) to six (which indicates DayOfWeek.Saturday).

Answer 2

DayOfWeek has sequential numbers.

Use a List<DayOfWeek>.

Go to definition shows:

// 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 3

You could create your own DayOfWeek enum if you need to use it like flags:

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

Answer 4

The DayOfWeek enumeration was designed to represent a single day of the week, not a set of days.

You don't get a compiler error for using & because enums are integers, but the operator doesn't do what you expect (unless you happen to only schedule events on Mondays, Tuesdays, or Thursdays).

If you want a bit flag, then declare a bit flag type, like Ray suggested.