Bitmask type to perform binary operations
It looks like you are misusing an enum as just a more cumbersome way to write a ulong.

If the days of the week are meant to be treated as a set rather than a single value (i.e., more like checkboxes than radio buttons), then you should be using the [Flags] attribute.  In fact, this is almost exactly the example given in the MSDN documentation:


[Flags]
enum Days2
{
    None = 0x0,
    Sunday = 0x1,
    Monday = 0x2,
    Tuesday = 0x4,
    Wednesday = 0x8,
    Thursday = 0x10,
    Friday = 0x20,
    Saturday = 0x40
}

class MyClass
{
    Days2 meetingDays = Days2.Tuesday | Days2.Thursday;
}



Personally, I'd write the constants using left-shift operators:

[Flags]
enum Days2
{
    None = 0,
    Sunday = 1 &lt;&lt; 0,
    Monday = 1 &lt;&lt; 1,
    Tuesday = 1 &lt;&lt; 2,
    Wednesday = 1 &lt;&lt; 3,
    Thursday = 1 &lt;&lt; 4,
    Friday = 1 &lt;&lt; 5,
    Saturday = 1 &lt;&lt; 6
}