The. Net get date belongs to the week ordinal of the year

Key code:
public static int WeekOfYear (DateTime dt, CultureInfo CI)
{
Mandatory setting Monday is the first day of the week
Return CI. Calendar.getweekofyear (DT, CI. Datetimeformat.calendarweekrule, Dayofweek.monday);
Set the first day of the week based on the culture information object
Return CI. Calendar.getweekofyear (DT, CI. Datetimeformat.calendarweekrule, Ci. Datetimeformat.firstdayofweek);
}

Invocation Example:

CultureInfo cultinfo = Cultureinfo.getcultureinfo ("ZH-CN");
Int week = WeekOfYear (DateTime.Now, cultinfo);
Console.WriteLine ("Date={0},weekofyear={1},day (of the Week) Is={2}", DateTime.Now.ToString (), Week, DateTime.Now.DayOfWeek.ToString ());

String datestr = "2017-01-01";
DateTime date1 = DateTime.Parse (Datestr, Cultinfo.datetimeformat);
Week = WeekOfYear (date1, cultinfo);
Console.WriteLine ("Date={0},weekofyear={1},day (of the Week) Is={2}", Datestr, Week,date1. Dayofweek.tostring ());

Datestr = "2017-12-31";
Date1 = DateTime.Parse (Datestr, Cultinfo.datetimeformat);
Week = WeekOfYear (date1, cultinfo);
Console.WriteLine ("Date={0},weekofyear={1},day (of the Week) Is={2}", Datestr, Week, Date1. Dayofweek.tostring ());

Output Result:

The. Net get date belongs to the week ordinal of the year