copying from a tab delimited text file to itself byattack

name    t loan period t loan amount
John    t 5 years     t 6000
Sarah   t 5 years     t 6000
Jane    t 1 month     t 100

name    t loan period t loan amount
John    t 5 years     t 6000
Sarah   t 5 years     t 6000
Jane    t 1 month     t 100
John    t 1 month     t 100
Sarah   t 1 month     t 100

Dim strData As String
    Dim i As Short
    Dim strLine() As String
    lngSize = 0

FileOpen(1, txtloanlistinput.Text, OpenMode.Input)
    While Not EOF(1)
        i = i + 1
        strData = LineInput(1)
    End While
    FileClose(1)
    ReDim loanlist(i)
    strData = ""
    lngSize = i
    i = 0
    FileOpen(2, txtloanlistinput.Text, OpenMode.Input)
    While Not EOF(2)
        i = i + 1
        strData = LineInput(2)
        If i = 1 Then
            strData = LineInput(2)
        End If
        strLine = Split(strData, Chr(9))
        loanlist(i).strName = strLine(0)
        loanlist(i).strLoanPeriod = strLine(1)
        loanlist(i).curLoanAmount = strLine(2)
    End While
    FileClose(1)
    FileClose(2)

OpenFileDialog dialog = new OpenFileDialog();
        dialog.ShowDialog();
        string filePath = dialog.FileName;
        //in this list we store the match of 5 years.
        List<string[]> fiveYears = new List<string[]>();
        //open a reader.
        StreamReader tr = new StreamReader(filePath);
        //reaing 1° line.
        string line=tr.ReadLine();
        while (line != null && line != "" && line != "n")
        {
            //split de line by tabs.
            string[] lineByTabs = line.Split('t');
           //if the second term equals '5 years'
            if (lineByTabs[1].Equals("5 years"))
            {
                //change from  5 years to 1 month, and to a lonan of 100.
                lineByTabs[1] = "1 month";
                lineByTabs[2] = "100";
                fiveYears.Add(lineByTabs);
            }
            line = tr.ReadLine();
        }
        //close reader
        tr.Close();
        //open the file and apend lines.
        TextWriter tw = new StreamWriter(filePath, true);

        foreach (string[] lines in fiveYears)
        {
            tw.WriteLine(lines[0] + "t" + lines[1] + "t" + lines[2]);
        }
        tw.Close();

    }

Dim dialog As OpenFileDialog = New OpenFileDialog
    Dim filePath, line As String
    Dim fiveYears As List(Of String()) = New List(Of String())
    Dim lineByTabs As String()
    Dim tr As StreamReader
    Dim tw As TextWriter
    dialog.ShowDialog()
    filePath = dialog.FileName

    tr = New StreamReader(filePath)

    line = tr.ReadLine()

    While Not line = ""

        lineByTabs = line.Split(vbTab)

        If lineByTabs(1).Equals("5 years") Then

            lineByTabs(1) = "1 month"
            lineByTabs(2) = "100"
            fiveYears.Add(lineByTabs)
        End If
        line = tr.ReadLine()
    End While

    tr.Close()

    tw = New StreamWriter(filePath, True)

    For Each lines As String() In fiveYears
        tw.WriteLine(lines(0) + vbTab + lines(1) + vbTab + lines(2))
    Next