quickscanning the code turned up no gotchas for me - as you isolated a stream and CRC that, first impulse is to suspect versioning. As this sounds stupid as well, setting up VMs with Dotnet 4.5 and another, older one and to compare CRC results done from "local VM system disc" and shared drives would be next step for me. PITA...


>This is something interesting. I am not sure if someone knows something about it.
>
>Recently, we moved into a new environment. Thus, the share drives are no longer Windows recognized drives but a NAS.
>
>There is one NAS device for the virtual environment, where, acting as a VMWare, allows us to have various share drives on one which might differ from the other one, as well as some specific configurations to each of them.
>
>The NetApp filers contain two environments, known as virtual filers. Both share the same physical interfaces, same memory, same heads and same cache.
>
>The NAS hardware being used is from NetApp company. They use a V-Series controller. They use disk rack called Disk Shelves. The data protocol is FC at the physical layer. This is like a special TCP. On top of FC, the protocol used is CIFS. This is what Windows uses.
>
>Since we are in that environment, we just discovered that the CRC32 returned for a JPG file no longer matches the CRC32 returned from the old environment. So, we are wondering if the .NET CRC32 being used is obtaining a different value from one technology to another.
>
>It is noted that at the same time, we also moved to .NET Framework 4.5. So, we are not sure if the new .NET Framework DLL are responding differently and that could be the source of the problem.
>
>Presently, this is not good. The production environment ends up with different values for the CRC32 where duplicate files should be recognized and they are not.
>
>Anyone has seen something like this before? Either the NAS technology is responsible for returning different CRC32 values or that we have new .NET DLL and this is something that I wouldn't be able to explain either.
>
>In case someone would worry, here is the CRC32 class of my framework:
>
>

>Imports System.IO
>
>Public Class CRC32
>
>    Public cMessage As String = ""
>    Public cFileName As String = ""
>    Public lLogError As Boolean = True
>    Public nCRC32 As Integer = 0
>    Public oApp As Framework.App = Nothing
>    Private cFileDoesNotExist As String = ""
>    Private nBufferSize As Integer = 1024
>    Private nCRC32Table() As Integer
>    Private nLanguage As Integer = 0
>    Private oProcess As Framework.LXProcess = Nothing
>
>    ' This is when we access the class in a desktop mode
>    Sub New(ByVal toApplication As Framework.App)
>        oApp = toApplication
>        nLanguage = oApp.nLanguage
>        Init()
>        Initialize()
>    End Sub
>
>    ' This is when we access the data provider in a Web mode
>    Public Sub New(ByVal toProcess As Framework.LXProcess)
>        oProcess = toProcess
>        oApp = oProcess.oApp
>        nLanguage = oProcess.nLanguage
>        Init()
>        Initialize()
>    End Sub
>
>    Private Function Init() As Boolean
>
>        ' Based on the language
>        Select Case nLanguage
>
>            ' English
>            Case 1
>                cFileDoesNotExist = "The file ##File## does not exist."
>
>                ' French
>            Case 2
>                cFileDoesNotExist = "Le fichier ##File## n'existe pas."
>
>                ' Spanish
>            Case 3
>                cFileDoesNotExist = "The file ##File## does not exist."
>
>                ' Portuguese
>            Case 4
>                cFileDoesNotExist = "The file ##File## does not exist."
>
>        End Select
>
>        Return True
>    End Function
>
>    ' This is the official polynomial used by CRC32 in PKZip.
>    ' Often the polynomial is shown reversed (04C11DB7).
>    ' Initialize
>    Private Function Initialize() As Boolean
>        Dim lnDWPolynomial As Integer = &HEDB88320
>        Dim lnCounter As Integer = 0
>        Dim lnCounter2 As Integer = 0
>        ReDim nCRC32Table(256)
>        Dim lnDWCRC As Integer
>
>        For lnCounter = 0 To 255
>            lnDWCRC = lnCounter
>
>            For lnCounter2 = 8 To 1 Step -1
>
>                If (lnDWCRC And 1) Then
>                    lnDWCRC = ((lnDWCRC And &HFFFFFFFE) \ 2&) And &H7FFFFFFF
>                    lnDWCRC = lnDWCRC Xor lnDWPolynomial
>                Else
>                    lnDWCRC = ((lnDWCRC And &HFFFFFFFE) \ 2&) And &H7FFFFFFF
>                End If
>
>            Next
>
>            nCRC32Table(lnCounter) = lnDWCRC
>        Next
>
>        Return True
>    End Function
>
>    ' This is the main method to call
>    Public Function GetCRC() As Boolean
>        Dim lcMessage As String = ""
>        Dim lnCounter As Integer = 0
>        Dim lnDelay As Integer = 250
>        Dim lnRetry As Integer = 8
>        Dim loStream As Stream = Nothing
>
>        ' Reset the values
>        cMessage = ""
>        nCRC32 = 0
>
>        ' We retry up to 8 times
>        For lnCounter = 1 To lnRetry
>
>            Try
>
>                ' If the file exists
>                If oApp.FileExist(cFileName) Then
>                    loStream = New FileStream(cFileName, FileMode.Open, FileAccess.Read, FileShare.Read, 8192)
>                Else
>                    lcMessage = oApp.StrTran(cFileDoesNotExist, "##File##", cFileName)
>
>                    ' If we log the error
>                    If lLogError Then
>
>                        ' Get the proper definition as per the current scope
>                        If oProcess Is Nothing Then
>                            oApp.ErrorSetup(, lcMessage)
>                        Else
>                            oProcess.ErrorSetup(, lcMessage)
>                        End If
>
>                    Else
>                        cMessage = lcMessage
>                        Return False
>                    End If
>
>                End If
>
>                Exit For
>
>            Catch loError As Exception
>
>                ' If we have not reached the maximum tries of 8, we retry
>                If lnCounter < 8 Then
>
>                    ' Wait for a timeout before retrying
>                    System.Threading.Thread.Sleep(lnDelay)
>
>                    Continue For
>                End If
>
>                ' If we log the error
>                If lLogError Then
>
>                    ' Get the proper definition as per the current scope
>                    If oProcess Is Nothing Then
>                        oApp.ErrorSetup(loError)
>                    Else
>                        oProcess.ErrorSetup(loError)
>                    End If
>
>                Else
>                    cMessage = loError.Message
>                    Return False
>                End If
>
>            End Try
>
>        Next
>
>        nCRC32 = GetCrc32(loStream)
>        loStream.Close()
>        Return True
>    End Function
>
>    Private Function GetCrc32(ByRef toStream As System.IO.Stream) As Integer
>        Dim lnCRC32Result As Integer = &HFFFFFFFF
>        Dim loBuffer(nBufferSize) As Byte
>        Dim lnReadSize As Integer = nBufferSize
>        Dim lnCount As Integer = 0
>        Dim lnCounter As Integer = 0
>        Dim lnLookup As Integer = 0
>
>        lnCount = toStream.Read(loBuffer, 0, lnReadSize)
>
>        Do While lnCount > 0
>
>            For lnCounter = 0 To lnCount - 1
>                lnLookup = (lnCRC32Result And &HFF) Xor loBuffer(lnCounter)
>
>                ' Nasty shr 8 with vb :/
>                lnCRC32Result = ((lnCRC32Result And &HFFFFFF00) \ &H100) And 16777215
>
>                lnCRC32Result = lnCRC32Result Xor nCRC32Table(lnLookup)
>            Next
>
>            lnCount = toStream.Read(loBuffer, 0, lnReadSize)
>        Loop
>
>        Return Not lnCRC32Result
>    End Function
>
>End Class
>

>
>That class remained unchanged since a very long time. So, this is the same code as before.