Optionally running some code on a background thread

Question

Is this a good method to optionally run some code on a background thread depending on a configuration setting? This will primarily be called from an ASP.NET front-end (although others are possible) under Framework 3.5. I'm attempting to keep this as DRY as possible.

Dim sendEmails = Sub() 
                     Dim emailToSend As New SendEmailRequest() 
                     TransferCommonValuesTo(emailToSend, request, sendingUser) 
                     usersToSendEmailTo.ForEach(Sub(u) 
                                                    TransferValuesTo(emailToSend, u, m_EmailMessageMerger.GetMergedMessage(request.Message, u)) 
                                                    m_EmailSender.Send(emailToSend) 
                                                End Sub) 
                 End Sub 


If cfg.SendBulkEmailUsingBackgroundThread Then 
    Dim worker As New Thread(sendEmails) 
    worker.IsBackground = True 
    worker.Start() 
Else 
    sendEmails() 
End If

Answer 1

Maybe.

Depends, as always, what happens if you get multiple threads running.

So you start this thread going, your code will move on, and if you start this again, and it hasn't finished the previous round of sending emails. What happens?

If its all thread safe, then no problem, but it might send some emails out of order. If its not thread safe, then hilarity ( or calamity ) ensues :-)