/// <summary>
/// Previous
/// </summary>
/// <param name="dt"></param>
/// <param name="dayOfWeek"></param>
/// <returns></returns>
public static DateTime PreviousDayOfWeek(this DateTime dt, DayOfWeek dayOfWeek)
{
var offset = DayOfWeekCalc.DaysBetween(dt.DayOfWeek, dayOfWeek);
offset = offset == 0 ? 7 : offset;
return(dt.AddDays(-offset));
}
/// <summary>
/// Get the day of the last specified week of the month.
/// </summary>
/// <param name="dt"></param>
/// <param name="dayOfWeek"></param>
/// <returns></returns>
public static DateTime LastDayOfMonth(this DateTime dt, DayOfWeek dayOfWeek)
{
var ret = dt.LastDayOfMonth();
return(DayOfWeekCalc.TryDaysBetween(ret.DayOfWeek, dayOfWeek, out var day) && day == 0
? ret
: ret.AddDays(-day));
}
/// <summary>
/// Get the day of the first specified week of the month.
/// </summary>
/// <param name="dt"></param>
/// <param name="dayOfWeek"></param>
/// <returns></returns>
public static DateTime FirstDayOfMonth(this DateTime dt, DayOfWeek dayOfWeek)
{
var ret = dt.FirstDayOfMonth();
return(DayOfWeekCalc.TryDaysBetween(ret.DayOfWeek, dayOfWeek, out var day) && day > 0
? ret.AddDays(day)
: ret);
}
public static DateInfo OffsetByDayOfWeek(DateInfo d, DayOfWeek dayOfWeek, int weekOffset)
{
var z = weekOffset > 0 ? 1 : -1;
var offset = DayOfWeekCalc.DaysBetween(d.DayOfWeek, dayOfWeek);
offset = offset == 0 ? 7 : offset;
return(d.OffsetBy(offset * z * weekOffset, DateTimeOffsetStyles.Day));
}
