MySQL Bugs: #6323: MySqlDataReader.GetBytes + .getChars throws Exception

Bug #6323	MySqlDataReader.GetBytes + .getChars throws Exception
Submitted:	29 Oct 2004 15:14	Modified:	9 Nov 2004 22:26
Reporter:	Jochen Hamleh	Email Updates:
Status:	Can't repeat	Impact on me:	None
Category:	Connector / NET	Severity:	S1 (Critical)
Version:	1.0.1.12619	OS:	Windows (Windows 2000)
Assigned to:	Reggie Burnett	CPU Architecture:	Any

Description:
Hi Reggie,

there seems to be a problem in the methods GetBytes and GetChars in the MySqlDataReader-Class that not occured in version 1.0.0.22722. Both methods always throwing an exception "System.ArgumentOutOfRangeException: Nicht-negative Zahl erforderlich; Parametername: count" at System.IO.BufferedStreamRead(Byte[] array, Int32 offset, Int32 count).
"Nicht-negative Zahl erforderlich" is german (I'm using a german .NET-Framework, because I am a german ;-) ) that means in english something like "no-negative number needed".

Could you help me ?

(Please excuse my bad english !)

Best regards,
Jochen Hamleh

How to repeat:
This is a function in VB.NET I use to write a file, that is saved in a MySQL 4.1.4_gamma database, to a given directory (= ziel). "OeffneVerbindung() gives me a valid Connection back in con. Try-Catch always runs to Catch at daten.GetBytes or daten.GetChars. This function had no problems with version 1.0.0.22722.

  Public Shared Function HoleBlob(ByVal tabelle As String, ByVal blobfeld As String, _
                                  ByVal zeilenID As String, ByVal ziel As String) As Boolean
    Dim rueckgabe As Boolean = True
    Dim con As MySqlConnection = OeffneVerbindung()
    Dim sqlSelect As MySqlCommand
    Dim daten As MySqlDataReader
    Dim blob(9999) As Byte
    Dim sql As String = "select " & blobfeld & " " & _
                        "from " & tabelle & " " & _
                        "where " & zeilenID
    Try
      sqlSelect = New MySqlCommand(sql, con)
      daten = sqlSelect.ExecuteReader(CommandBehavior.SequentialAccess)
      If daten.Read() Then
        File.Delete(ziel)
        Dim fs As New FileStream(ziel, FileMode.OpenOrCreate, FileAccess.Write)
        Dim bw As New BinaryWriter(fs)
        Dim bufferSize As Integer = 10000
        'Dim outbyte(bufferSize - 1) As Byte
        Dim outbyte(bufferSize - 1) As Char
        Dim retval As Long
        Dim startIndex As Long = 0
        'retval = daten.GetBytes(0, startIndex, outbyte, 0, bufferSize)
        retval = daten.GetChars(0, startIndex, outbyte, 0, bufferSize)
        While retval = bufferSize
          bw.Write(outbyte)
          bw.Flush()

          startIndex = startIndex + bufferSize
          'retval = daten.GetBytes(0, startIndex, outbyte, 0, bufferSize)
          retval = daten.GetChars(0, startIndex, outbyte, 0, bufferSize)
        End While

        bw.Write(outbyte, 0, retval)
        bw.Flush()

        bw.Close()
        fs.Close()

        rueckgabe = True
      Else
        rueckgabe = False
      End If
    Catch ex As Exception
      rueckgabe = False
    Finally
      If Not daten Is Nothing Then
        daten.Close()
      End If
      If Not sqlSelect Is Nothing Then
        sqlSelect.Dispose()
      End If
      con.Close()
      con.Dispose()
    End Try
    Return rueckgabe

Not enough information was provided for us to be able
to handle this bug. Please re-read the instructions at
http://bugs.mysql.com/how-to-report.php

If you can provide more information, feel free to add it
to this bug and change the status back to 'Open'.

Thank you for your interest in MySQL.

Additional info:

I am unable to repeat this behavior.  If you want to send me a small application that shows this behavior, I will be happy to look at it again.

Hi Reggie,

I found an easy solution for this problem. The problem only occured when the ExecuteReader-Method of the MySqlCommand-Class is called with parameter CommandBehavior.SequentialAccess. Without parameters the method works fine.

Is there probably a problem with the SequentialAccess-Behavior of the ExecuteReader-Method ?

You can set the status of this bug to closed.

(Now I have another problem with the bug #6322 ...)

Best regards,
Jochen