Imports System.IO
Imports System
Imports System.Text
Imports Microsoft.VisualBasic.FileSystem
 
dim fs as filestream
    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) _
      Handles MyBase.Load
        Me.fs = New FileStream("E:\test.txt", FileMode.Open, _
        FileAccess.ReadWrite)
    End Sub
 
    Private Sub cmdAppend_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button2.Click
        On Error Resume Next
        Dim str As String = "dein text" & vbCrLf
        fs.Seek(0, SeekOrigin.End)
        Dim info As Byte() = New UTF8Encoding(True).GetBytes(str)
        fs.Write(info, 0, info.Length)
    End Sub
 
    Private Sub cmdInfo_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        Dim barr(fs.Length) As Byte
        Dim frminfo As New Form2
        fs.Seek(0, SeekOrigin.Begin)
        fs.Read(barr, 0, fs.Length)
        Dim str As String = New UTF8Encoding(True).GetChars(barr)
        frminfo.TextBox1.Text = str
        frminfo.ShowDialog()
    End Sub
 
    Private Sub Form1_Disposed(ByVal sender As Object, ByVal e As _
      System.EventArgs) Handles MyBase.Disposed
        On Error Resume Next
        Me.fs.Close()
    End Sub

Nichts ist umsonst!