CODEWITHSUNDEEP
c#vb.netwinformsasync-await
Lee Morgan
Lee Morgan

Reputation: 112

C# Async/Await SmtpClient.SendMailAsync

I have written a simple class for me to send reports which works well, however I now need to incorporate a log to check whether the send was successful or not.

A quick brief on my app: It has a main form that you can manually run the reports via buttons and if the app is run from the command line then the form is hidden.

When the form is shown the SmtpClient.SendComplete event fires, but when the form is hidden it does not and also doesn't send the email. I have tried every which way to get it to work. 

public static async Task SendAsync(string sendTo, string subject, string body = "", string attachment = "")
{
#if (DEBUG)
    // If in DEBUG mode then send reports to lee.
    sendTo = "developer";
#endif
    try
    {
        SmtpClient client = new SmtpClient("smtp.server", 587)
        { Credentials = new NetworkCredential("username", "password") };
        MailMessage message = new MailMessage
        { From = new MailAddress("mailFrom") };
        message.To.Add(sendTo);
        message.Subject = subject;
        message.Body = body;
        if (!string.IsNullOrEmpty(attachment))
            message.Attachments.Add(new Attachment(attachment));
        client.SendCompleted += (s,e) =>
            {
                if (e.Error != null)
                {
                    Logger.FileLog(message.Subject, e.Error.ToString());
                }
                else
                {
                    Logger.FileLog(message.Subject, "Message Sent");
                }
                client.Dispose();
                message.Dispose();
            };
        Logger.FileLog(_subject, "Running Async");
        await client.SendMailAsync(message);

        Logger.FileLog(_subject, "Finished");
    }
    catch (Exception e)
    {
        Logger.FileLog(subject, $"Error {e.HResult}, {e.Message}, {e.InnerException.ToString()}");
    }
}

I have tried async Task, async void, SendAsync, SendMailAsync, loops to wait for a callback.

Some of the logging is there just so I can see how far it got when running from the command line and it only ever gets as far as "Running Async" which is before it tries to send the email.

The code for detecting whether to show or hide the form as requested, the original project was written in VB, the above code is in a class library which was working until I tried to run Async.

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
    If CommandLineArgs.Count > 0 Then
        Visible = False
        RunSilent = True
        ParseCommandLine()
        Close()
    Else
        'Update to add from db, XML or Excel
        Dim t As Task = Task.Run(
            Sub()
                LoadReports()
            End Sub)
        t.Wait()
    End If
End Sub

Any help or advice will be greatly appreciated.

Upvotes: 1

Views: 1873

Answers (1)

Nkosi
Nkosi

Reputation: 246998

You close right after processing command line, so chances are that you are not awaiting the method and Close is being invoked before the email can be sent.

assuming ParseCommandLine and LoadReports are async functions then you should await them in the event handler

Private Async Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
    If CommandLineArgs.Count > 0 Then
        Visible = False
        RunSilent = True
        Await ParseCommandLine() 'wait for task to complete then close
        Close()
    Else
        'Update to add from db, XML or Excel
        Await LoadReports()
    End If
End Sub

Note the removal of .Wait() blocking call that could cause deadlock when mixed with async calls.

Reference Async/Await - Best Practices in Asynchronous Programming

Upvotes: 1

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