What are best practices for using SmtpClient, SendAsync and Dispose under .NET 4.0

Question

I\'m a bit perplexed on how to manage SmtpClient now that it is disposable, especially if I make calls using SendAsync. Presumably I should not call Dispose until SendAsync

Answer 1

Note: .NET 4.5 SmtpClient implements async awaitable method SendMailAsync. For lower versions, use SendAsync as described below.

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You should always dispose of IDisposable instances at the earliest possibility. In the case of async calls, this is on the callback after the message is sent.

var message = new MailMessage("from", "to", "subject", "body"))
var client = new SmtpClient("host");
client.SendCompleted += (s, e) => {
                           client.Dispose();
                           message.Dispose();
                        };
client.SendAsync(message, null);

It's a bit annoying the SendAsync doesn't accept a callback.