md5 hash for file without File Attributes

Posted by Glennular on Stack Overflow See other posts from Stack Overflow or by Glennular
Published on 2010-04-28T15:50:03Z Indexed on 2010/04/28 15:53 UTC
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Using the following code to compute MD5 hashs of files:

 Private _MD5Hash As String
 Dim md5 As New System.Security.Cryptography.MD5CryptoServiceProvider
 Dim md5hash() As Byte
 md5hash = md5.ComputeHash(Me._BinaryData)
 Me._MD5Hash = ByteArrayToString(md5hash)

  Private Function ByteArrayToString(ByVal arrInput() As Byte) As String
     Dim sb As New System.Text.StringBuilder(arrInput.Length * 2)
     For i As Integer = 0 To arrInput.Length - 1
       sb.Append(arrInput(i).ToString("X2"))
     Next
     Return sb.ToString().ToLower
  End Function

We are getting different hashes depending on the create-date and modify-date of the file. We are storing the hash and the binary file in a SQL DB. This works fine when we upload the same instance of a file. But when we save a new instance of the file from the DB (with today's date as the create/modify) on the file-system and then check the new hash versus the MD5 stored in the DB they do not match, and therefor fail a duplicate check.

How can we check for a file hash excluding the file attributes? or is there a different issue here?

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