getWeek(DateTime.Now.Date, "WWYY", 0);

     /// <summary>/// 获取周期/// </summary>/// <param name="CurrentDate">填写计算日期</param>/// <param name="Format">YYYY,YY,WW,MM,DD</param>/// <param name="AddDay">增加周期日期</param>/// <returns></returns>public string getWeek(DateTime CurrentDate, string Format, int AddDay = 0){string YYYY, YY, MM, DD, WW;CurrentDate = CurrentDate.AddDays(AddDay);//CurrentDate = DateTime.Parse("2014-12-29");YYYY = CurrentDate.Year.ToString();YY = YYYY.Substring(2, 2);MM = CurrentDate.Month.ToString().PadLeft(2, '0');DD = CurrentDate.Day.ToString().PadLeft(2, '0');WW = "";if (Format.IndexOf("WW") > -1){int StartWeek = 4;DateTime CurrentStartDate = new DateTime(CurrentDate.Year, 1, 1);DateTime CurrentFirstWeekDate = getFirstWeekDate(CurrentStartDate, StartWeek);int DayCount = 0, WeekCount = 0, WeekDayCount = 0, WeekNum = 0, YearNum = 0, MonthNum = 0;if (CurrentDate >= CurrentFirstWeekDate){DateTime NextStartDate = new DateTime(CurrentDate.Year + 1, 1, 1);DateTime NextFirstWeekDate = getFirstWeekDate(NextStartDate, StartWeek);if (CurrentDate >= NextFirstWeekDate){DayCount = (CurrentDate - NextFirstWeekDate).Days + 1;YearNum = NextStartDate.Year;MonthNum = NextStartDate.Month;}else{DayCount = (CurrentDate - CurrentFirstWeekDate).Days + 1;YearNum = CurrentStartDate.Year;MonthNum = CurrentStartDate.Month;}}else{DateTime PreviouStartDate = new DateTime(CurrentDate.Year - 1, 1, 1);DateTime PreviouFirstWeekDate = getFirstWeekDate(PreviouStartDate, StartWeek);DayCount = (CurrentDate - PreviouFirstWeekDate).Days + 1;YearNum = PreviouStartDate.Year;MonthNum = PreviouStartDate.Month;}WeekCount = (int)Math.Floor(DayCount / 7.0);WeekDayCount = DayCount % 7;WeekNum = WeekCount + (int)Math.Ceiling(WeekDayCount / 7.0);YYYY = YearNum.ToString();YY = YYYY.Substring(2, 2);MM = MonthNum.ToString().PadLeft(2, '0');WW = WeekNum.ToString().PadLeft(2, '0');}return Format.Replace("YYYY", YYYY).Replace("YY", YY).Replace("MM", MM).Replace("DD", DD).Replace("WW", WW);}/// <summary>/// 获取当前日期第一周 开始的日期/// </summary>/// <param name="StartDate">计算日期</param>/// <param name="StartWeek">起始周期</param>/// <returns>第一周日期</returns>public DateTime getFirstWeekDate(DateTime StartDate, int StartWeek = 4){int CurrentWeek = (int)StartDate.DayOfWeek == 0 ? 7 : (int)StartDate.DayOfWeek;int CurrentWeekDiff = CurrentWeek <= StartWeek ? -CurrentWeek + 1 : 7 - CurrentWeek + 1;DateTime CurrentFirstWeekDate = StartDate.AddDays(CurrentWeekDiff);return CurrentFirstWeekDate;}