How do I dispose System.Net.Mail.MailMessage in VB when using SendAsync - vb.net

Question

I have not managed to find a conclusive answer for this on here or in MSDN. When using the following code, if I try to dispose the message after sending the asynch mail then I get a System.ObjectDisposedException: Cannot access a disposed object. This is when the microsoft example suggests disposing.
I can't dispose the message in the callback because it is out of scope. I have tried using a module level Mail message but get the same results. If I don't dispose the message everything works fine but this is not good practice. Please advice the best place to dispose the mail message.
Public Sub SendEmailWithReport(ByVal v_objEmailAddress As System.Collections.Generic.List(Of String), ByVal v_strSubject As String,
ByVal v_strBody As String, ByVal v_strFileName As String, ByVal v_intContentID As Integer,
ByVal v_strType As String) Implements IMessagingPlatform.SendEmailWithReport
Dim objMessage As New MailMessage
Dim objAttachment As New Attachment(v_strFileName, MediaTypeNames.Application.Pdf)
Try
'configure e-mail addresses and add attachment
With objMessage
For Each strAddress As String In v_objEmailAddress
.To.Add(strAddress)
Next
.Attachments.Add(objAttachment)
End With
SetUpAsynchEmail(objMessage, v_strSubject, v_strBody, v_strFileName, v_intContentID, v_strType)
Catch ex As Exception
Trace.WriteLine(DateTime.Now().ToString("dd/MM/yyyy HH:mm:ss.fff") & " : Failed to setup e-mail with report: " & ex.Message.ToString, "ERR")
Finally
'objMessage.Dispose() *disposing here gives System.ObjectDisposedException: Cannot access a disposed object.**
'objAttachment.Dispose()
End Try
End Sub
Private Sub SetUpAsynchEmail(ByVal v_objMessage As MailMessage, ByVal v_strSubject As String, ByVal v_strBody As String,
ByVal v_strFileName As String, ByVal v_intContentID As Integer, ByVal v_strType As String)
Dim intID As Integer
Try
Dim basicAuthenticationInfo As New System.Net.NetworkCredential(mstrUserName, mstrPassword)
Dim objClient As New SmtpClient()
'configure mail message
With v_objMessage
.IsBodyHtml = True
.Subject = v_strSubject
.Body = v_strBody
If mstrFromEmailName <> "" Then
.From = New MailAddress(mstrFromEmailAddress, mstrFromEmailName)
Else
.From = New MailAddress(mstrFromEmailAddress)
End If
End With
'configure mail client
With objClient
.Host = mstrSMTPHost
.UseDefaultCredentials = False
.Credentials = basicAuthenticationInfo
.EnableSsl = True
.Port = mintSMTPPort
End With
' Set the method that is called back when the send operation ends.
AddHandler objClient.SendCompleted, AddressOf SendCompletedCallback
'Generate a unique message number
intID = mobjContainer.AddUnsentMail(v_intContentID, v_strType, v_strFileName)
If intID > -1 Then
objClient.SendAsync(v_objMessage, intID)
End If
'v_objMessage.Dispose() **disposing here gives System.ObjectDisposedException: Cannot access a disposed object.
Catch ex As Exception
Trace.WriteLine(DateTime.Now().ToString("dd/MM/yyyy HH:mm:ss.fff") & " : Failed to setup e-mail: " & ex.Message.ToString, "ERR")
Finally
End Try
End Sub
Private Sub SendCompletedCallback(ByVal v_objSender As SmtpClient, ByVal e As AsyncCompletedEventArgs)
' Get the unique identifier for this asynchronous operation.
Dim strMessageID As String = CStr(e.UserState)
Try
If e.Cancelled Then
Trace.WriteLine(DateTime.Now().ToString("dd/MM/yyyy HH:mm:ss.fff") & " : E-mail cancelled for message with ID " &
strMessageID, "ERR")
End If
If e.Error IsNot Nothing Then
Trace.WriteLine(DateTime.Now().ToString("dd/MM/yyyy HH:mm:ss.fff") & " : Failed to send e-mail with ID " &
strMessageID & ", " & e.Error.ToString(), "ERR")
'E-mail error - update table
mobjContainer.UpdateUnsentMail(CInt(strMessageID))
Else
'E-mail success - delete record from table
mobjContainer.DeleteUnsentMailItem(CInt(strMessageID))
Trace.WriteLineIf(mobjLogTrace.LogEvents = True And mobjLogTrace.LogDetail >= 4, DateTime.Now().ToString("dd/MM/yyyy HH:mm:ss.fff") &
" : E-mail with ID " & strMessageID & " successfully sent", "EVT")
End If
Catch objException As Exception
Trace.WriteLine(DateTime.Now().ToString("dd/MM/yyyy HH:mm:ss.fff") & " : Failed to send e-mail with ID " &
strMessageID & ", " & objException.ToString(), "ERR")
Finally
v_objSender.Dispose()
End Try
End Sub

Answer 1

If you created a class to hold both intID and your v_objMessage and passed this as the second parameter in your objClient.SendAsync() call you would have access to both the ID and the message in the SendCompletedCallback() sub. You could then call .Dispose on the message in your Finally block.