如何获取每月和每年中特定日期的日期？

Question

Just want to get the date of Monday, Wednesday and Saturday of every month in the years. i tried to managed it this way;

DateTime today = DateTime.UtcNow;
int deltaMonday = DayOfWeek.Monday - today.DayOfWeek;
var monday = today.AddDays(deltaMonday);


int deltaWednesday = DayOfWeek.Wednesday - today.DayOfWeek;
var wednesday = today.AddDays(deltaWednesday);

int deltaSaturday = DayOfWeek.Saturday - today.DayOfWeek;
var saturday = today.AddDays(deltaSaturday);

But i want to show the next (eg) monday date if this (week) monday is passed away and similarly for wednesday and saturday too. If the (current) month is passed away, then next month days should be displayed. Is there any shorter way to get or change my code?

Answer 1

Try this -

 DateTime today = DateTime.UtcNow;
 int deltaMonday = DayOfWeek.Monday - today.DayOfWeek;
 var monday = today.AddDays(deltaMonday += deltaMonday < 0 ? 7 : 0);

 int deltaWednesday = DayOfWeek.Wednesday - today.DayOfWeek;
 var wednesday = today.AddDays(deltaWednesday += deltaWednesday < 0 ? 7 : 0);

 int deltaSaturday = DayOfWeek.Saturday - today.DayOfWeek;
 var saturday = today.AddDays(deltaSaturday += deltaSaturday < 0 ? 7 : 0);

In short, if the day is passed away, that is the difference is negative, then just add 7 days to it.

Do similar things if you need to check for months.

Answer 2

try this-

 Public DateTime GetNextWeekday(DayOfWeek day)
 {
     DateTime result = DateTime.Now.AddDays(1);
     while( result.DayOfWeek != day )
          result = result.AddDays(1);
     return result;
 }

 DateTime deltaMonday=GetNextWeekday(1)
 DateTime deltaWednesday=GetNextWeekday(3)
 DateTime deltaSaturday=GetNextWeekday(6)

Answer 3

If you know how many days ahead you need to look, you could use linq. The code below finds all Monday, Wednesday and Saturday in the next 100 days:

var daysAhead = Enumerable.Range(0, 100);
var dates = daysAhead.Select (a => DateTime.Today.AddDays(a))
                         .Where (a => a.DayOfWeek == DayOfWeek.Monday ||
                                      a.DayOfWeek == DayOfWeek.Wednesday ||
                                      a.DayOfWeek == DayOfWeek.Saturday ).ToList();