I need to delete something from a .txt file but it leaves an empty line! I have set code to stop this but it deletes something else

Question

I need to set this piece of code in vb so that a user can delete a specific string from a .txt document. But when they do, it leaves an empty line. I then got more code to stop this but then it deletes something else within the file with the empty line.

Code:

        If (txtDelUser.Text = "admin" Or txtDelUser.Text = "guest") Then
        rtbOutput2.Text = "You tried to delete: " + txtDelUser.Text + ". But the user is protected by default."
    Else

        Dim ln As Integer = 1
        rtbOutput.Text.First(Of Text = Text.CopyTo.ClipBoard

        'Removes the selected username from list of usernames
        Dim lines As New List(Of String)
        Using sr As New StreamReader("C:\ProgramData\Hax Client\User Data\All Usernames.txt")
            While Not sr.EndOfStream
                lines.Add(sr.ReadLine)
            End While
        End Using

        For Each line As String In lines
            If line.Contains(txtDelUser.Text) Then
                lines.Remove(line)

                Exit For 'must exit as we changed the iteration 
            End If
        Next
        'End of removing the line
        Dim fs As New FileStream("C:\ProgramData\Hax Client\User Data\All Usernames.txt", FileMode.Append)
        Dim sw As New StreamWriter(fs)

        Dim foundBlank As Boolean
        For Each line As String In lines
            If line.Length > 0 Then
                sw.WriteLine(line)
                ' Reset blank line flag
                foundBlank = False
            Else
                If Not foundBlank Then
                    ' Blank line: write first one
                    sw.WriteLine(line)
                    ' Set flag to indicate that blank line was found
                    foundBlank = True
                End If
            End If
        Next
        sw.Close()
        fs.Close()
        My.Computer.FileSystem.FileExists("C:\ProgramData\Hax Client\User Data\" + txtDelUser.Text)
        My.Computer.FileSystem.DeleteFile("C:\ProgramData\Hax Client\User Data\" + txtDelUser.Text + ".txt")
        rtbOutput2.Text = "Deleted user: " + txtDelUser.Text
    End If

Text file:

admin
guest
testing

Can you either look over my code or give me some code that will allow me to delete from the .txt file, by whats entered into a textbox, without leaving an empty or a way to get rid of the empty line.

Thanks!

Answer 1

You can store the items that you want to write back to file in another list, linesToKeep, like this:

Dim linesToKeep As New List(Of String)

For Each line As String In lines
    If Not line.Contains(txtDelUser.Text) Then
        linesToKeep.Add(line) 
    End If
Next

' Write all lines in linesToKeep back to file
For Each line As String In lines
    sw.WriteLine(line)
Next

UPDATE:

Here is what the full code should look like using this solution applied to the code posted:

If (txtDelUser.Text = "admin" Or txtDelUser.Text = "guest") Then
    rtbOutput2.Text = "You tried to delete: " + txtDelUser.Text + ". But the user is protected by default."
Else
    Dim ln As Integer = 1
    rtbOutput.Text.First(Of Text = Text.CopyTo.ClipBoard

    'Removes the selected username from list of usernames
    Dim lines As New List(Of String)
    Using sr As New StreamReader("C:\ProgramData\Hax Client\User Data\All Usernames.txt")
        While Not sr.EndOfStream
            lines.Add(sr.ReadLine)
        End While
    End Using

    ' Instead of removing items from the list we read from file
    ' we are going to keep track of what we want to keep and write back to file later
    Dim linesToKeep As New List(Of String)

    For Each line As String In lines
        If Not line.Contains(txtDelUser.Text) Then
            linesToKeep.Add(line) 
        End If
    Next

    Dim fs As New FileStream("C:\ProgramData\Hax Client\User Data\All Usernames.txt", FileMode.Append)
    Dim sw As New StreamWriter(fs)

    ' Write all lines in linesToKeep back to file
    For Each line As String In lines
        sw.WriteLine(line)
    Next        

    sw.Close()
    fs.Close()
    My.Computer.FileSystem.FileExists("C:\ProgramData\Hax Client\User Data\" + txtDelUser.Text)
    My.Computer.FileSystem.DeleteFile("C:\ProgramData\Hax Client\User Data\" + txtDelUser.Text + ".txt")
    rtbOutput2.Text = "Deleted user: " + txtDelUser.Text
End If