Extracting specific lines from one text file to other text file - vb.net

Question

I want to extract some specific lines from a text file to other text file. i am using the following code
Imports System.IO
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim Tr As IO.TextReader = System.IO.File.OpenText("C:\Assignment.txt")
For c As Integer = 1 To 10
If c = 7 Then
Dim MyFileLine As String = Split(Tr.ReadToEnd(), vbCrLf)(c) & vbCrLf
Tr.Close()
Dim TW As System.IO.TextWriter
'Create a Text file and load it into the TextWriter
TW = System.IO.File.CreateText("C:\Assignment1.txt")
TW.WriteLine(MyFileLine)
'Flush the text to the file
TW.Flush()
'Close the File
TW.Close()
End If
Next c
End Sub
End Class
But this code extract only the line no 7 where i want to extract the 8th,9th,10th,14th,15th,16th, lines also . Please guide me the right solution. Thank u in advance.

Answer 1

There seems to be several issues here. I will correct them and then explain below:
Imports System.IO
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim currentLine As String
Dim lineCounter As Integer = 1
Dim lineNumbersRequired As List(Of Integer) = New List(Of Integer)
lineNumbersRequired.Add(7)
lineNumbersRequired.Add(8)
lineNumbersRequired.Add(9)
lineNumbersRequired.Add(10)
lineNumbersRequired.Add(14)
lineNumbersRequired.Add(15)
lineNumbersRequired.Add(16)
Dim TW As System.IO.TextWriter
'Create a Text file and load it into the TextWriter
TW = System.IO.File.CreateText("C:\Assignment1.txt")
Using Tr As IO.TextReader = New IO.StreamReader("C:\Assignment.txt")
While Not Tr.EndOfStream
If lineNumbersRequired.Contains(lineCounter) Then
Dim MyFileLine As String = Split(currentLine, vbCrLf)(c) & vbCrLf
TW.WriteLine(MyFileLine)
End If
lineCounter = lineCounter + 1
End While
End Using
TW.Flush()
'Close the File
TW.Close()
End Sub
End Class
NOTE: Code not tested, but should be pretty close if you do get a few compile errors!
Ok then, just a quick rundown of what I did here:
Changed the For Loop into a while because you had the for loop running from 1 To 10, so even if it worked, then you would have never read past the 10th line in your file. So I have changed it to a while loop that will end when the TextReader has read all lines in the file. Also the current line read from the file has been added to a new variable called currentLine.
The new currentLine variable is now used to populate the lines of your writing file.
I have added a list of Integers that will hold the line numbers you want to keep, then within the while loop I have a counter that counts each line as it is processed and if this counter is inside the list of line numbers you want to save into your output file, then it will output the current line.
Let me know how you get on, and if you need more of an explanation on any of it then please ask.