以前的一个项目中遇到过要核对条码的校验码的需求，感觉有时候还是非常有用的，下面提供代码，代码版本为VB.net：

 //根据输入的的条码来计算该条码的校验位

Private Function GetCheckDigit(Byal strCode As String) As String

        Dim intCurVal As Int16 = 0

        Dim intChksum As Int16 = 0

        Dim chrCur As String

        Dim intPos As Int16

        'Check for invalid characters and calculate check sum

        For intPos = 1 To Len(strCode)

            chrCur = Mid(strCode, intPos, 1)

            Select Case chrCur

                Case "0" To "9"

                    intCurVal = Val(chrCur)

                Case "A" To "Z"

                    intCurVal = Asc(chrCur) - 55

                Case "-"

                    intCurVal = 36

                Case "."

                    intCurVal = 37

                Case " "

                    intCurVal = 38

                Case "$"

                    intCurVal = 39

                Case "/"

                    intCurVal = 40

                Case "+"

                    intCurVal = 41

                Case "%"

                    intCurVal = 42

                Case Else

            End Select

            intChksum = intChksum + intCurVal

        Next

        intChksum = intChksum Mod 43

        Select Case intChksum

            Case 0 To 9

                Return intChksum.ToString()

            Case 10 To 35

                Return Chr(intChksum + 55)

            Case 36

                Return "-"

            Case 37

                Return "."

            Case 38

                Return " "

            Case 39

                Return "$"

            Case 40

                Return "/"

            Case 41

                Return "+"

            Case 42

                Return "%"

            Case Else

        End Select

        Return "0"

    End Function