open

'add at top of source codes
Imports System.IO


'add on a button
Dim ofd As New OpenFileDialog
        ofd.Title = "select your text file"
        ofd.ShowDialog()
        Dim sr As New StreamReader(ofd.FileName)
        Do While (sr.Peek > -1)
            listbox.items.add = (sr.ReadLine)
        Loop
        sr.Close()