Obtain period by subtract start datetime and end datetime with workday - vb.net

Question

I am trying to implement a method in VB.NET that could subtract a start datetime and datetime, and result this specific string period "D.HH:mm:ss", observing that the day doesn't have 24 hours, but only 8 hours.
My function to do the subtract return only the diff in hours and as decimal:
Public Function WH(ByVal date1 As Date, ByVal date2 As Date,
Optional ByVal considerwk As Boolean = True) As Decimal
Dim ini_tim As DateTime = DateTime.Parse("08:00")
Dim end_tim As DateTime = DateTime.Parse("18:00")
'//RESULT
Dim _res As Integer
'//WHILE INITIAL LESS THAN END...
Do While date1 <= date2
'//INSIDE INTERVAL?
If Hour(date1) >= Hour(ini_tim) And Hour(date1) <= Hour(end_tim) Then
'//CONSIDER WORKDAY?
If considerwk = True Then
'//IF NOT SATURDAY OR SUNDAY
If Weekday(date1) <> vbSaturday And Weekday(date1) <> vbSunday Then
'//ADD +1 IN RESULT
_res += 1
End If
Else
'//ADD +1 IN RESULT
_res += 1
End If
End If
'//ADD A MINUTE IN THE DATE
date1 = DateAdd("n", 1, date1)
Loop
'//RETURN THE DIFF IN DEC
Return CDec(_res / 60)
End Function
Hope that you can help me!
Thanks!

Answer 1

Something to consider...
With your current code:
Hour(date1) <= Hour(end_tim)
A time of 18:01 would be considered "inside the interval" when it's actually after the end time!
Try something more like below. It'll be accurate down to the second and can handle it if your start/stop times are not exactly at the top of the hour (like 08:30 to 18:30):
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim dt1 As DateTime = DateTime.Now
Dim dt2 As DateTime = dt1.AddDays(5).AddHours(4).AddMinutes(39).AddSeconds(17)
Dim ts As TimeSpan = WH(dt1, dt2, True)
Dim strFormattedTotal As String = String.Format("{0}.{1}:{2}:{3}", ts.Days, ts.Hours.ToString("00"), ts.Minutes.ToString("00"), ts.Seconds.ToString("00"))
Label1.Text = "Total: " & strFormattedTotal
Label2.Text = "Total Hours: " & ts.TotalHours
End Sub
Public Function WH(ByVal date1 As Date, ByVal date2 As Date, Optional ByVal considerwk As Boolean = True) As TimeSpan
Static ini_tim As DateTime = DateTime.Parse("08:00")
Static end_tim As DateTime = DateTime.Parse("18:00")
Dim TS As New TimeSpan
Do While date1 < date2
If date1.TimeOfDay >= ini_tim.TimeOfDay AndAlso date1.TimeOfDay <= end_tim.TimeOfDay Then
If considerwk Then
If date1.DayOfWeek <> DayOfWeek.Saturday AndAlso date1.DayOfWeek <> DayOfWeek.Sunday Then
TS = TS.Add(TimeSpan.FromSeconds(1))
End If
Else
TS = TS.Add(TimeSpan.FromSeconds(1))
End If
End If
date1 = date1.AddSeconds(1)
Loop
Return TS
End Function