Заменить содержимое файла - Visual Basic .NET

 Dim SaveFileDialog1 As New SaveFileDialog()
        SaveFileDialog1.InitialDirectory = "C:\"
        SaveFileDialog1.Title = "Сохранить в файл"
        SaveFileDialog1.FileName = "povtor.txt"
        SaveFileDialog1.Filter = "txt files (*.txt)|*.txt|All files (*.*)|*.*"
        SaveFileDialog1.InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)
        SaveFileDialog1.CreatePrompt = True
        SaveFileDialog1.OverwritePrompt = True
        If SaveFileDialog1.ShowDialog = DialogResult.OK Then
            Dim sr As System.IO.StreamWriter
            Label7.Text = SaveFileDialog1.FileName
            sr = My.Computer.FileSystem.OpenTextFileWriter(Label7.Text, True)
            sr.Write(TextBox3.Text)
            sr.Close()
        End If