Check for valid IMEI

Question

Hi,

does somebody knows how to check for a valid IMEI?

I have found a function to check on this page: http://www.dotnetfunda.com/articles/article597-imeivalidator-in-vbnet-.aspx

But it returns false for valid IMEI's (f.e. 352972024585360). I can validate them online on this page: http://www.numberingplans.com/?page=analysis&sub=imeinr

What is the correct way(in VB.Net) to check if a given IMEI is valid?

Regards, Tim

PS: This function from above page must be incorrect in some way:

   Public Shared Function isImeiValid(ByVal IMEI As String) As Boolean
        Dim cnt As Integer = 0
        Dim nw As String = String.Empty
        Try
            For Each c As Char In IMEI
                cnt += 1
                If cnt Mod 2 <> 0 Then
                    nw += c
                Else
                    Dim d As Integer = Integer.Parse(c) * 2 ' Every Second Digit has to be Doubled
                    nw += d.ToString() ' Genegrated a new number with doubled digits
                End If
            Next
            Dim tot As Integer = 0
            For Each ch As Char In nw.Remove(nw.Length - 1, 1)
                tot += Integer.Parse(ch) ' Adding all digits together
            Next
            Dim chDigit As Integer = 10 - (tot Mod 10) ' Finding the Check Digit my Finding the Remainder of the sum and subtracting it from 10
            If chDigit = Integer.Parse(IMEI(IMEI.Length - 1)) Then ' Checking the Check Digit with the last digit of the Given IMEI code
                Return True
            Else
                Return False
            End If
        Catch ex As Exception
            Return False
        End Try
    End Function

EDIT: by the way, this is my "checkIMEI"-Function:

    Public Shared Function checkIMEI(ByRef IMEI As String) As Boolean
        Const allowed As String = "0123456789"

        Dim cleanNumber As New System.Text.StringBuilder
        For i As Int32 = 0 To IMEI.Length - 1
            If (allowed.IndexOf(IMEI.Substring(i, 1)) >= 0) Then
                cleanNumber.Append(IMEI.Substring(i, 1))
            End If
        Next

        If cleanNumber.Length <> 15 Then
            Return False
        Else
            IMEI = cleanNumber.ToString
        End If

        For i As Int32 = cleanNumber.Length + 1 To 16
            cleanNumber.Insert(0, "0")
        Next

        Dim multiplier As Int32, digit As Int32, sum As Int32, total As Int32 = 0
        Dim number As String = cleanNumber.ToString()

        For i As Int32 = 1 To 16
            multiplier = 1 + (i Mod 2)
            digit = Int32.Parse(number.Substring(i - 1, 1))
            sum = digit * multiplier
            If (sum > 9) Then
                sum -= 9
            End If
            total += sum
        Next

        Return (total Mod 10 = 0)
    End Function

Answer 1

IMEI numbers are validated using the Luhn algorithm. The linked page has implementations in various languages.