GregorianCalendar去年的一周

Question

我有一個Excel工作表，其列日期從2003年開始（格式：2015/02/10），並且列銷售。 我想提取（去年，當前一周，今天的名稱）銷售數字。 就像今天是2月12日星期四，那么相當於去年的“星期四”是在2月13日。我已經嘗試了下面的代碼但是我得到錯誤“無法轉換字符串”星期四“加倍”任何想法如何？ 謝謝

 Dim MyCalendar As Calendar = New GregorianCalendar
    Dim culture = New System.Globalization.CultureInfo("EN-US")
    dim eventcal as new datatable
    Dim dayname As String = culture.DateTimeFormat.GetDayName(Now.DayOfWeek)

    Dim lastCurrentweek = MyCalendar.GetWeekOfYear(
      Now,
      CalendarWeekRule.FirstFourDayWeek,
      DayOfWeek.Sunday)
    Dim lastCurrentyear = MyCalendar.GetYear(Now) - 1
        dim dayrecord = (From Row In eventcal.AsEnumerable
           Where MyCalendar.GetWeekOfYear(Row.Field(Of DateTime)("date"),
           CalendarWeekRule.FirstFourDayWeek,
            DayOfWeek.Sunday) = Currentweek And MyCalendar.GetYear(Row.Field(Of DateTime)("date")) = lastCurrentyear And MyCalendar.GetDayOfWeek(Row.Field(Of DateTime)("date")) = dayname
           Select Row.Field(Of Double)("sales"))

Answer 1

對於它可能感興趣的人，這里是你如何得到相當於去年或前一年的今天。 感謝tommytwotrain提供此解決方案

Private Function Date2Weekday(ByVal d As Date, ByVal y As Integer) As Date
    'determine week
    Dim weekNumber As Integer = Math.Ceiling(d.Day / 7)
    'determine day number
    Dim daynumber1 As Integer = Weekday(d)
    'determine target first day of month
    Dim targetDay1 As Date = New DateTime(y, d.Month, 1)
    Dim targetDay1Number As Integer = Weekday(targetDay1)
    Dim dt As Integer = (weekNumber * 7) + (daynumber1 - targetDay1Number)+1
    If dt > weekNumber * 7 Then dt -= 7
 Date2Weekday = New DateTime(y, d.Month, dt)     
 End Function

Private Function salescalendar(ByVal dtduty As DataTable) As DataTable
   Dim eventcal As New DataTable
    Dim lastyear = MyCalendar.GetYear(Now) - 1
    Dim todays As Date = Now.Date
 Dim dayrecord = (From Row In eventcal.AsEnumerable
                 Where Row.Field(Of DateTime)("date") = Date2Weekday(todays, lastyear)
                Select Row.Field(Of Double)("sales")) 
  end function