[RESOLVED] VB.NET search text file and remove only first found duplicate.

[mikeg71]

Hi All - I am using this code to find and remove duplicates, but now what I need to do is search for the duplicate, but only remove the first duplicate found in the text file. I could have up to 3-4 duplicates in the file. Having a hard time searching for this.

Dim filename As String = "c:\scripts\scan.txt"
File.WriteAllLines(filename, File.ReadAllLines(filename).Where(Function(l) l <> TB_Search.Text))

[dday9]

Your title is a bit different than what your code is doing. It looks like you want to remove only the first instance of a line in a text file that matches the text in your TextBox.

If that's the case, then you can do this:

Private Sub RemoveMatchingLineFromFile(filename As String, term As String)
    Dim lines = New List(Of String)(IO.File.ReadAllLines(filename))

    Dim indexToRemove = -1
    For index = lines.Count - 1 To 0 Step -1
        Dim line = lines(index)
        If (line = term)) Then
            indexToRemove = index
        End If
    Next

    If (indexToRemove > -1) Then
        lines.RemoveAt(indexToRemove)
    End If

    IO.File.WriteAllLines(filename, lines)
End Sub

' RemoveMatchingLineFromFile("c:\scripts\scan.txt", TB_Search.Text)

This loops from the last line to the first line, sets the index that will be removed if the currently iterated line matches the search term, optionally removes the line, and then updates the file's text.

Edit - I just realized you can make this more concise by using the FindIndex method:

Private Sub RemoveMatchingLineFromFile(filename As String, term As String)
    Dim lines = New List(Of String)(IO.File.ReadAllLines(filename))

    Dim indexToRemove = lines.FindIndex(Function(line) line = term)
    If (indexToRemove > -1) Then
        lines.RemoveAt(indexToRemove)
    End If

    IO.File.WriteAllLines(filename, lines)
End Sub

It's the same concept only the looping is taken care of under the hood.

[mikeg71]

dday9 - Thank you, this is EXACTLY what I needed. Much appreciated