Dim x As New chat
 
If IO.File.Exists(Nickname & ".txt") Then
Dim flstr As FileStream = New FileStream(App_Path() & Nickname & ".txt", _
  FileMode.OpenOrCreate, FileAccess.Write)
Dim w As StreamWriter = New StreamWriter(flstr)
If TextBox1.Text <> String.Empty Then
w.BaseStream.Seek(0, SeekOrigin.End)
w.WriteLine(Nickname & " sagt:" & vbNewLine & Nachricht & vbNewLine)
w.Close()
flstr.Close()
End If
 
Else
IO.File.WriteAllText(App_Path() & Nickname & ".txt", Nickname & " sagt:" & _
  vbNewLine & Nachricht & vbNewLine)
x.Text = Nickname
x.Show()
End If

CheckForIllegalCrossThreadCalls = False
Dim text As String = IO.File.ReadAllText(App_Path() & Me.Text & ".txt")
RichTextBox1.Text = text