/// <summary>
/// Returns the end of week from the supplied date
/// </summary>
public static DateTime EndOfWeek(this DateTime instance, DayOfWeek? on = null)
{
DayOfWeek day = on.GetValueOrDefault(DayOfWeek.Saturday);
int days = day - instance.DayOfWeek;
if (days < 0) days += 7;
days = days * -1;
return new DateTime(instance.Year, instance.Month, instance.Day, 23, 59, 59, 999).AddDays(days);
}
/// <summary>
/// Returns the start of week from the supplied date
/// </summary>
public static DateTime StartOfWeek(this DateTime instance, DayOfWeek? on = null)
{
DayOfWeek day = on.GetValueOrDefault(DayOfWeek.Sunday);
int days = instance.DayOfWeek - day;
if (days < 0) days += 7;
days = days * -1;
return new DateTime(instance.Year, instance.Month, instance.Day, 0, 0, 0, 0).AddDays(days);
}
/// <summary>
/// <paramref name="weekRule"/>, <paramref name="firstDayOfWeek"/>에 해당하는 <see cref="WeekOfYearRuleKind"/>를 판단합니다.
/// </summary>
/// <param name="weekRule">한해의 첫주를 산정하는 규칙</param>
/// <param name="firstDayOfWeek">한주의 첫번째 요일</param>
public static WeekOfYearRuleKind GetWeekOfYearRuleKind(CalendarWeekRule? weekRule = null,
DayOfWeek? firstDayOfWeek = null) {
if(weekRule.GetValueOrDefault(DateTimeFormatInfo.CurrentInfo.CalendarWeekRule) == CalendarWeekRule.FirstFourDayWeek &&
firstDayOfWeek.GetValueOrDefault(DateTimeFormatInfo.CurrentInfo.FirstDayOfWeek) == DayOfWeek.Monday)
return WeekOfYearRuleKind.Iso8601;
return WeekOfYearRuleKind.Calendar;
}