ASP.Net + Vb.Net อยากจะทำ textfile ให้เป็นรูปแบบ binary

  If dr.HasRows Then

                    Check_Floder()
                    '............................................................. ถ้าไม่มี Directory นี้
                    If System.IO.Directory.Exists(InvFile4BookFriend & "\backup\" & dateCreate & "\") = False Then
                        'สร้าง Directory นี้
                        System.IO.Directory.CreateDirectory(InvFile4BookFriend & "\backup\" & dateCreate & "\")
                    End If


                    '..............................................................................

                    Delete_File()

                    '........................................................... เขียนใน Directory นี้
                    SW = New StreamWriter(InvFile4BookFriend & "\backup\" & dateCreate & "\N_Tran.txt")
                    '..............................................................................

                    While dr.Read

                        With DataVar

                            No = dr(0)
                            Array(index) = dr(0)
                            If IsDBNull(dr.Item("INVNUM")) = False Then .INVNUM = dr.Item("INVNUM") Else .INVNUM = ""
                            If IsDBNull(dr.Item("store_id")) = False Then .store_id = dr.Item("store_id") Else .store_id = ""
                            If IsDBNull(dr.Item("Date")) = False Then .[Date] = dr.Item("Date") Else .[Date] = ""
                            If IsDBNull(dr.Item("Deduct")) = False Then .Deduct = dr.Item("Deduct") Else .Deduct = 0
                            If IsDBNull(dr.Item("SUBTOT")) = False Then .SUBTOT = dr.Item("SUBTOT") Else .SUBTOT = 0
                            If IsDBNull(dr.Item("DEDTOT")) = False Then .DEDTOT = dr.Item("DEDTOT") Else .DEDTOT = 0
                            If IsDBNull(dr.Item("TOTAL")) = False Then .TOTAL = dr.Item("TOTAL") Else .TOTAL = 0
                            If IsDBNull(dr.Item("CU_CODE")) = False Then .CU_CODE = dr.Item("CU_CODE") Else .CU_CODE = ""

                            'dr.Item("") กรณีที่ยุคนละตารางในใส่item
                            'ชื่อฟิล.ฟิลนั้นถ้ายุมีเหมือนกันในตาราง()
                            SW.Write(.INVNUM & "|")
                            SW.Write(.store_id & "|")
                            SW.Write(.[Date] & "|")
                            SW.Write(.Deduct & "|")
                            SW.Write(.SUBTOT & "|")
                            SW.Write(.DEDTOT & "|")
                            SW.Write(.TOTAL & "|")

                            If Enterr <> Count Then
                                SW.WriteLine(.CU_CODE)
                            Else
                                SW.Write(.CU_CODE)
                            End If

                        End With