Best way to optimise For Loops and Do Until Loops [closed] - vb.net

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I have the following code that searches through folder directories in a DataGridView table, and puts all files of the wanted format into a list, it also gathers a list of their last modified date for later use in the application.
The code works, but it is sore on the eyes. I want to tidy up the following loops to improve efficiency - what I mean is that I have a For loop within a For loop that creates the list of filenames, then I have two separate Do Until loops that search through the list from start to finish to pick out file names that need adjustment.
I would be very interested to learn a better way of achieving the same result, as my knowledge of efficiency in coding is quite elementary. Basically, can this be done in one or two loops, as the idea of looping through the Lists twice seems inefficient?
Public Class
Private Sub btnDirectory_Click(sender As Object, e As EventArgs) Handles btnDirectory.Click
Dim FileNames As New List(Of String)
Dim FileDates As New List(Of Date)
Dim DocNo As String
Dim rowCheck As String
Dim ProjectNo As String = "1111"
Dim FileNameCheck As String
Dim str As String
Dim k As Integer = 0
Dim i As Integer
Dim j As Integer
Dim CorrectType As Boolean = False
'The first loop grabs all files of the wanted format from a datagridview table containing all directories to be checked
For Each rw In Background.Table1.Rows
rowCheck = Background.Table1(0, k).Value
If Not String.IsNullOrEmpty(rowCheck) Then
For Each file As String In My.Computer.FileSystem.GetFiles(Background.Table1(0, k).Value)
CorrectType = False
FileNameCheck = IO.Path.GetFileNameWithoutExtension(file)
If FileNameCheck.Contains(ProjectNo) AndAlso FileNameCheck.Contains("-") AndAlso Not String.IsNullOrEmpty(FileNameCheck) AndAlso FileNameCheck.Contains(" ") Then
DocNo = FileNameCheck.Substring(0, FileNameCheck.IndexOf(" "))
If FileNameCheck.Substring(0, FileNameCheck.IndexOf("-")) = ProjectNo AndAlso CountLetters(DocNo) = 3 Then
CorrectType = True
End If
End If
If CorrectType = True Then
FileNames.Add(FileNameCheck)
FileDates.Add(IO.File.GetLastWriteTime(file))
End If
Next
End If
k += 1
Next
'The next loop tidies up the file formats that contain a "-00-" in their names
j = FileNames.Count
i = 0
Do
str = FileNames(i)
If str.Contains("-00-") Then
FileNames(i) = RemoveChar(str, "-00-") ' RemoveChar is a function that replaces "-00-" with a "-"
End If
i += 1
Loop Until i = j
i = 0
j = FileNames.Count
'Finally, this loop checks that no two files have the exact same name, and gets rid of one of them if that is the case
Do
Dim st1 As String = FileNames(j - 1)
Dim st2 As String = FileNames(j - 2)
If st1 = st2 Then
FileNames.RemoveAt(j - 1)
FileDates.RemoveAt(j - 1)
End If
j -= 1
Loop Until j = 1
End Sub
End Class

Answer 1

The code is certainly hard on the eyes.
the For Each rw loop does not use rw. You could replace this with a loop such as:
For k = 1 to Background.Table1.Rows.Count
' Do things here
Next k
You assign rowCheck and use it once, but you missed the opportunity to reuse it in the For Each file line.
Where you have CorrectType = True you can easily place the corresponding code instead.
If FileNameCheck.Substring(0, FileNameCheck.IndexOf("-")) = ProjectNo AndAlso CountLetters(DocNo) = 3 Then
CorrectType = True
End If
End If
If CorrectType = True Then
FileNames.Add(FileNameCheck)
FileDates.Add(IO.File.GetLastWriteTime(file))
End If
becomes:
If FileNameCheck.Substring(0, FileNameCheck.IndexOf("-")) = ProjectNo AndAlso CountLetters(DocNo) = 3 Then
FileNames.Add(FileNameCheck)
FileDates.Add(IO.File.GetLastWriteTime(file))
End If
I must admit, the next two loops made my eyes bleed (figuratively, not literally).
j = FileNames.Count
i = 0
Do
str = FileNames(i)
If str.Contains("-00-") Then
FileNames(i) = RemoveChar(str, "-00-") ' RemoveChar is a function that replaces "-00-" with a "-"
End If
i += 1
Loop Until i = j
becomes
for i = 1 to FileNames.Count
str = FileNames(i)
If str.Contains("-00-") Then
FileNames(i) = RemoveChar(str, "-00-") ' RemoveChar is a function that replaces "-00-" with a "-"
End If
Next I
And
i = 0
j = FileNames.Count
'Finally, this loop checks that no two files have the exact same name, and gets rid of one of them if that is the case
Do
Dim st1 As String = FileNames(j - 1)
Dim st2 As String = FileNames(j - 2)
If st1 = st2 Then
FileNames.RemoveAt(j - 1)
FileDates.RemoveAt(j - 1)
End If
j -= 1
Loop Until j = 1
becomes
'Finally, this loop checks that no two files have the exact same name, and gets rid of one of them if that is the case
For j = FileNames.Count - 1 to 1 Step -1 ' Check my counting here - stop at 1, 2 or 0?
Dim st1 As String = FileNames(j)
Dim st2 As String = FileNames(j - 1)
If st1 = st2 Then
FileNames.RemoveAt(j)
FileDates.RemoveAt(j)
End If
Next j