[RESOLVED] how to calculate EAN8 barcode checksum

hello,
in my app the user scans a barcode (EAN8) and i need my app to verify that barcode is correct,that is to check the checksum.

i found online just the algorithm for the EAN13 but no EAN8.Someone worked with this one before?

thanks:wave:

This is not a VB.NET question. If you have the algorithm and you need help to implement it in VB.NET, THAT is a suitable question for this forum.

mmmm, yes , you're right, i think i was searching someone who worked with both vb.net and barcodes.
my best regards.

Code:

---

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        MessageBox.Show(EAN8_Checksum("5512345"))
    End Sub

    Private Function EAN8_Checksum(ByVal EAN8_Barcode As String) As String
        'http://www.barcodeisland.com/ean8.phtml

        Dim ChecksumCalculation As Integer = 0

        Dim Position As Int32 = 1
        For i As Integer = EAN8_Barcode.Length - 1 To 0 Step -1
            If Position Mod 2 = 1 Then
                'odd position
                ChecksumCalculation += Convert.ToInt32(EAN8_Barcode.Substring(i, 1)) * 3
            Else
                'even position
                ChecksumCalculation += Convert.ToInt32(EAN8_Barcode.Substring(i, 1)) * 1
            End If
            Position += 1
        Next

        Dim Checksum As Integer = 10 - (ChecksumCalculation Mod 10)

        Return Convert.ToString(Checksum)
    End Function

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thank you,the URL you inserted in you're code really help me alot.;)

Wish I had paid attention to the dates... This does 8 and 13

@MattP - got me ;)

Code:

---

    Private Function EAN_Checksum(ByVal EAN_Barcode As String, _
                                  Optional eanType As Integer = 8) As String
        Dim oddW As Integer 'odd weighting
        Dim evenW As Integer 'even weighting
        Dim isOdd As Boolean

        If eanType = 8 Then 'EAN8
            If EAN_Barcode.Length <> 7 Then
                'error code needed
                Throw New Exception
            End If
            oddW = 3
            evenW = 1
            isOdd = True
        ElseIf eanType = 13 Then 'EAN13
            If EAN_Barcode.Length <> 12 Then
                'error code needed
                Throw New Exception
            End If
            oddW = 1
            evenW = 3
            isOdd = False
        Else
            'error code needed
            Throw New Exception
        End If
        Dim Checksum As Integer
        'make sure the barcode is numeric
        If Long.TryParse(EAN_Barcode, Nothing) Then
            For Each c As String In EAN_Barcode.Reverse
                If isOdd Then
                    'odd position
                    Checksum += Integer.Parse(c) * oddW
                Else
                    'even position
                    Checksum += Integer.Parse(c) * evenW
                End If
                isOdd = Not isOdd
            Next
            Checksum = 10 - (Checksum Mod 10)
        Else
            'error code needed
            Throw New Exception
        End If
        Return Checksum.ToString
    End Function

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