สอบถามครับ ผมต้องการหาค่าจำนวนวันที่ทำงานครับ VB.NET

Public Overloads Function DateDiff( _
    ByVal Interval As [ DateInterval | String ], _
    ByVal Date1 As DateTime, _
    ByVal Date2 As DateTime, _
    Optional ByVal DayOfWeek As FirstDayOfWeek = FirstDayOfWeek.Sunday, _
    Optional ByVal  WeekOfYear As FirstWeekOfYear = FirstWeekOfYear.Jan1 _
) As Long

Dim diff As Long DateDiff(Convert.ToDateTime("01-Jan-2016"),DateTime.Now.Date,"d")

' The following statements set datTim1 to a Thursday 
' and datTim2 to the following Tuesday. 
Dim datTim1 As Date = #1/4/2001#
Dim datTim2 As Date = #1/9/2001#
' Assume Sunday is specified as first day of the week. 
Dim wD As Long = DateDiff(DateInterval.Weekday, datTim1, datTim2)
Dim wY As Long = DateDiff(DateInterval.WeekOfYear, datTim1, datTim2)