Does anyone know how to calculate Longitudinal Redundancy Check(LRC) in
VB.NET?
I am trying to send Visa-II formatted even parity message to a credit
card processor and am not sure how to calculate the LRC which needs to
be appended to the message.

Any pointers would be most helpful.
Thanks in advance.
Sankalp

I believe that the lrc byte is just the xor of all the data bytes.

Here is the code that I am using:
        GenerateMessageETX() - This function returns the credit card
data and the ETX chanracter in the string format.
Then I create an HTTPWebRequest to the credit card payment gateway.


        Dim message As String = pageData

        Dim j As Integer

        Dim LRC As Byte = "0"

        For j = 0 To message.Length - 1
            Dim chr As Char = message.Substring(j, 1)
            LRC = LRC Xor Convert.ToByte(chr)
        Next

Is this the LRC value or do i need to do something else.

Please guide-have been stuck in this for some time now.

Sankalp

I don't like this:
   Dim LRC As Byte = "0"

It probably gives a compiler error.  I would code like this:

      Dim message As String = pageData
      Dim lrc As Integer = 0
      For j As Integer = 0 To message.Length - 1
        lrc = lrc Xor AscW(message.Chars(j))
      Next

At this point, my guess is that you should transmit this string:
   message & Chr(lrc)
It is your pageData string with one lrc byte appended.

Thanks A, tried this but doesnt work. Now I am beginning to doubt the
servers as well. They have given us 2 servers to test with one being
the backup server. But, both the servers are returning different
responses to the same message. I guess i will have to verify this with
the company. Thanks for your help again :-)

Sankalp

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