Imports System.IO

Public Class Form1
  Inherits System.Windows.Forms.Form

Vom Windows Form Designer generierter Code

 'Datei neu anlegen und Text hineinschreiben
  Private Sub Button1_Click(ByVal sender As System.Object, _
          ByVal e As System.EventArgs) Handles Button1.Click
    Dim FiStr As FileStream = _
          New FileStream(TextBox1.Text, FileMode.Create)
    Dim StrWr As StreamWriter = New StreamWriter(FiStr)
    StrWr.WriteLine(TextBox2.Text)
    StrWr.Close()
  End Sub

 'Text anfügen an bestehende Datei
 ' oder die Datei neu anlegen, wenn sie nicht existiert
 ' und Text hineinschreiben
  Private Sub Button2_Click(ByVal sender As System.Object, _
          ByVal e As System.EventArgs) Handles Button2.Click
    Dim FiStr As FileStream = _
          New FileStream(TextBox1.Text, FileMode.Append)
    Dim StrWr As StreamWriter = New StreamWriter(FiStr)
    StrWr.WriteLine(TextBox2.Text)
    StrWr.Close()
  End Sub

 'Datei lesen
  Private Sub Button3_Click(ByVal sender As System.Object, _
          ByVal e As System.EventArgs) Handles Button3.Click
    Try
      Dim FiStr As FileStream = _
            New FileStream(TextBox1.Text, FileMode.Open)
      Dim StrRe As StreamReader = New StreamReader(FiStr)
      Dim i As Integer
      ListBox1.Items.Clear()
      Do Until StrRe.Peek() = -1
        ListBox1.Items.Add(StrRe.ReadLine)
        i += 1
      Loop
      StrRe.Close()
    Catch except As Exception
      MsgBox(except.Message & vbNewLine & _
              "Erstellen Sie zunächst mit <Anfügen> oder " & _
              "<Überschreiben> die Datei", _
              MsgBoxStyle.Exclamation)
    End Try
  End Sub

  Private Sub Form1_Load(ByVal sender As System.Object, _
          ByVal e As System.EventArgs) Handles MyBase.Load
      TextBox1.Text = Environment.CurrentDirectory & "\Test.dat"
      TextBox2.Text = "Hallo"
  End Sub

  Private Sub Button4_Click(ByVal sender As System.Object, _
          ByVal e As System.EventArgs) Handles Button4.Click
    Me.Close()
  End Sub
End Class