public static IEnumerable <DateTime> DatesOnSelectedDays(this DateRange dateRange, DaySelection daySelection) => dateRange.Start.DatesOnSelectedDaysAfter(daySelection) .TakeWhile(date => date <= dateRange.End);
public static IEnumerable <DateTime> DatesOnSelectedDaysAfter(this DateTime dateRange, DaySelection daySelection)
{
if (!daySelection.Any())
{
yield break;
}
var dayDates = new List <DateTime>(capacity: 7);
var date = dateRange;
for (int i = 0; i < 7; i++)
{
if (daySelection.Contains(date.DayOfWeek))
{
dayDates.Add(date);
yield return(date);
}
date = date.AddDays(1);
}
while (true)
{
for (int i = 0; i < dayDates.Count; i++)
{
date = dayDates[i] = dayDates[i].AddDays(7);
yield return(date);
}
}
}
