VBA Code not consolidating all duplicates - vba

Question

I hope you can help. I have a piece of code and it works relatively well.
What it does is it allows a user to click on a command button which opens up a dialog box. The user then selects another excel sheet, then the code identifies duplicates consolidates these duplicates creating a new row of data with the earliest available start date and latest available end date and then deletes the duplicates
So in Pic 1 you can see the selected sheet has duplicate entries and multiple start and end dates for these duplicate entries
Pic 1
Pic 2 shows the sheet after the code has executed
You can see in Pic 2 that the duplicates have been consolidated and a row of data with the earliest start date and latest end date is left
Agnholt Jørgen Steen is correct
Andersen Anders Nyboe is correct
But it only works if the duplicates are directly under eachother if they are not as in the case with
Christensen Tove and Christensen Trine Tang my code is unable to identify the duplicates and it does not consolidate or work the dates.
Can my code be amended to fix this issue of duplicates not being directly underneath each other?
My code is below as always and all help is greatly appreciated.
MY CODE
Sub Open_Workbook_Dialog()
Dim strFileName As String
Dim wkb As Workbook
Dim wks As Worksheet
Dim lastRow As Long
Dim r As Long
MsgBox "Select Denmark File" '<--| txt box for prompt to pick a file
strFileName = Application.GetOpenFilename(FileFilter:="Excel Files,*.xl*;*.xm*") '<--| Opens the file window to allow selection
Set wkb = Application.Workbooks.Open(strFileName)
Set wks = ActiveWorkbook.Sheets(1)
lastRow = wks.UsedRange.Rows.Count
For r = lastRow To 3 Step -1
' Identify Duplicate
If wks.Cells(r, 1) = wks.Cells(r - 1, 1) _
And wks.Cells(r, 2) = wks.Cells(r - 1, 2) _
And wks.Cells(r, 3) = wks.Cells(r - 1, 3) _
And wks.Cells(r, 4) = wks.Cells(r - 1, 4) _
And wks.Cells(r, 5) = wks.Cells(r - 1, 5) _
And wks.Cells(r, 6) = wks.Cells(r - 1, 6) _
And wks.Cells(r, 7) = wks.Cells(r - 1, 7) Then
' Update Start Date on Previous Row
If CDate(wks.Cells(r, 8)) < CDate(wks.Cells(r - 1, 8)) Then
wks.Cells(r - 1, 8) = wks.Cells(r, 8)
End If
' Update End Date on Previous Row
If CDate(wks.Cells(r, 9)) > CDate(wks.Cells(r - 1, 9)) Then
wks.Cells(r - 1, 9) = wks.Cells(r, 9)
End If
' Delete Duplicate
Rows(r).Delete
End If
Next
End Sub
So i have amended the code to sort Column B but it still leave duplicates
my Code with the sort added is below again any help is greatly appreciated.
CODE
Sub Open_Workbook_Dialog()
Dim strFileName As String
Dim wkb As Workbook
Dim wks As Worksheet
Dim lastRow As Long
Dim r As Long
MsgBox "Select Denmark File" '<--| txt box for prompt to pick a file
strFileName = Application.GetOpenFilename(FileFilter:="Excel Files,*.xl*;*.xm*") '<--| Opens the file window to allow selection
Set wkb = Application.Workbooks.Open(strFileName)
Set wks = ActiveWorkbook.Sheets(1)
lastRow = wks.UsedRange.Rows.Count
With ActiveWorkbook.Sheets(1)
.Unprotect
lastcol = .Cells(1, .Columns.Count).End(xlToLeft).Column
.Range("A1").Resize(79, lastcol).Sort Key1:=Range("B1"), _
Order1:=xlAscending, _
Header:=xlGuess, _
OrderCustom:=1, _
MatchCase:=False, _
Orientation:=xlTopToBottom, _
DataOption1:=xlSortNormal
End With
For r = lastRow To 3 Step -1
' Identify Duplicate
If wks.Cells(r, 1) = wks.Cells(r - 1, 1) _
And wks.Cells(r, 2) = wks.Cells(r - 1, 2) _
And wks.Cells(r, 3) = wks.Cells(r - 1, 3) _
And wks.Cells(r, 4) = wks.Cells(r - 1, 4) _
And wks.Cells(r, 5) = wks.Cells(r - 1, 5) _
And wks.Cells(r, 6) = wks.Cells(r - 1, 6) _
And wks.Cells(r, 7) = wks.Cells(r - 1, 7) Then
' Update Start Date on Previous Row
If CDate(wks.Cells(r, 8)) < CDate(wks.Cells(r - 1, 8)) Then
wks.Cells(r - 1, 8) = wks.Cells(r, 8)
End If
' Update End Date on Previous Row
If CDate(wks.Cells(r, 9)) > CDate(wks.Cells(r - 1, 9)) Then
wks.Cells(r - 1, 9) = wks.Cells(r, 9)
End If
' Delete Duplicate
Rows(r).Delete
End If
Next
End Sub

Answer 1

Your code removes duplicates that are one after another. Those duplicates don't touch, thus aren't deleted.
This way of doing is faster (linear and not quadratic like normal duplicate finding code) but does not work if some duplicates don't touch)
Solution : You should sort the table (with regard to all columns, not just the first one) before running the code. This way duplicates will always touch.