Salvare il contenuto di una textbox

Dim save As New SaveFileDialog()
       Dim mystreamwriter As System.IO.StreamWriter
       save.Filter = "Text |*.txt"
       save.CheckPathExists = True
       save.Title = "Save Files"
       save.ShowDialog(Me)
       Try
           mystreamwriter = System.IO.File.AppendText(save.FileName)
           mystreamwriter.Write(c.Text)
           mystreamwriter.Flush()
       Catch ex As Exception

       End Try