DayOfWeek get the next DayOfWeek(Monday,Tuesday...Sunday)

Question

Is there a way to summarize this code into 1-2 lines?

My goal is to return, for example, I have a DayOfWeek which is Monday, I want to get the day after that (Tuesday) or n days after that.

         switch (_RESETDAY)
        {
            case DayOfWeek.Monday:
                _STARTDAY = DayOfWeek.Tuesday;
                break;
            case DayOfWeek.Tuesday:
                _STARTDAY = DayOfWeek.Wednesday;
                break;
            case DayOfWeek.Wednesday:
                _STARTDAY = DayOfWeek.Thursday;
                break;
            case DayOfWeek.Thursday:
                _STARTDAY = DayOfWeek.Friday;
                break;
            case DayOfWeek.Friday:
                _STARTDAY = DayOfWeek.Saturday;
                break;
            case DayOfWeek.Saturday:
                _STARTDAY = DayOfWeek.Sunday;
                break;
            case DayOfWeek.Sunday:
                _STARTDAY = DayOfWeek.Monday;
                break;
            default:
                _STARTDAY = DayOfWeek.Tuesday;
                break;
        }

score 10 · Accepted Answer · answered Sep 28 '15 at 15:39

This is just an int enumeration, ranging from Sunday (0) to Saturday (6), as per MSDN:

The DayOfWeek enumeration represents the day of the week in calendars that have seven days per week. The value of the constants in this 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).

So simple math should do it:

DayOfWeek nextDay = (DayOfWeek)(((int)_RESETDAY + 1) % 7);

Replace + 1 with + n if that's what you need.

This is the best one. It accounts for switching from Saturday to Sunday — David P, Sep 28 '15 at 15:40

score 4 · Answer 2 · answered Sep 28 '15 at 15:37

4

Yes.

(DayOfWeek)((int)(_RESETDAY+1)%7)

answered Sep 28 '15 at 15:37

Ian Newson

7,679
2
47
80

score 2 · Answer 3 · answered Sep 28 '15 at 15:44

2

same result as the addition and modulo stuff answered above, but more readable imho:

day = (day == DayOfWeek.Saturday) ? DayOfWeek.Sunday : day + 1;

Obvious code intent is always more enjoyable.

answered Sep 28 '15 at 15:44

Jonesopolis

25,034
12
68
112

Mulflar · Answer 4 · 2015-09-28T15:46:11.367

0

    static DayOfWeek dayplus (DayOfWeek day)
    {
        if (day == DayOfWeek.Saturday)
            return DayOfWeek.Sunday;
        else
            return day + 1;
    }

For example

Console.WriteLine(dayplus(DayOfWeek.Sunday));

Will return monday

edited Sep 28 '15 at 15:46

answered Sep 28 '15 at 15:43

Mulflar

424
9
22

Yes, I noticed the problem with saturday because here week starts on Monday, but I edited – Mulflar Sep 28 '15 at 15:46

score 0 · Answer 5 · edited May 09 '16 at 17:21

The general case solution uses modulo arithemtics:

  DayOfWeek _RESETDAY = ...;
  int shift = 1; // can be positive or negative

  // + 7) % 7 to support negative shift´s
  DayOfWeek result = (DayOfWeek) ((((int)_RESETDAY + shift) % 7 + 7) % 7);

probably, the best implmentation is to hide the combersome formula in the extension method:

 public static class DayOfWeekExtensions {
   public static DayOfWeekShift(this DayOfWeek value, int shift) {
     return (DayOfWeek) ((((int)value + shift) % 7 + 7) % 7);
   }
 }

 ...

 var result = _RESETDAY.Shift(1);

and slightly reduced (only works in all cases if negative shift isn't lower than -7) :

     return (DayOfWeek)(((int)value + shift + 7) % 7);

@Ian Newson: when `shift < 0` then `%7` can return a *negative value* - so `+7` (and the second `% 7`) should be added — Dmitry Bychenko, Sep 28 '15 at 16:01

DayOfWeek get the next DayOfWeek(Monday,Tuesday...Sunday)

5 Answers5

Related