(C#) Async Task Chain

Demonstrates how to combine a sequence of asynchronous tasks into a single task chain to be run in a background thread.

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// All Chilkat classes can be unlocked at once at the beginning of a program
// by calling UnlockBundle.  It requires a Bundle unlock code.
Chilkat.Global chilkatGlob = new Chilkat.Global();
bool success = chilkatGlob.UnlockBundle("Anything for 30-day trial.");
if (success != true) {
    Debug.WriteLine(chilkatGlob.LastErrorText);
    return;
}

Chilkat.MailMan mailman = new Chilkat.MailMan();

// Set the POP3 server's hostname
mailman.MailHost = "pop.someMailServer.com";

// Set the POP3 login/password and any other requirements..
mailman.PopUsername = "myLogin";
mailman.PopPassword = "myPassword";
mailman.PopSsl = true;
mailman.MailPort = 995;

// Connect to the POP3 server:
success = mailman.Pop3BeginSession();
if (!success) {
    Debug.WriteLine(mailman.LastErrorText);
    return;
}

// Get the number of messages in the mailbox.
int numMessages = mailman.GetMailboxCount();
if (numMessages == 0) {
    Debug.WriteLine("No email messages in the POP3 mailbox.");
    return;
}

Chilkat.TaskChain taskChain = new Chilkat.TaskChain();

// Create async task objects to fetch each email message
// by its sequence number
int i;
Chilkat.Task task = null;

for (i = 1; i <= numMessages; i++) {

    task = mailman.FetchByMsgnumAsync(i);
    if (mailman.LastMethodSuccess == false) {
        Debug.WriteLine(mailman.LastErrorText);
        return;
    }

    // Append each task to the task chain.
    success = taskChain.Append(task);
    if (!success) {
        Debug.WriteLine(taskChain.LastErrorText);
        return;
    }

}

// At this point, no tasks have actually started running.
// All we've done so far is to create tasks for the work that will be done
// when the task chain is run.

// Start the task chain running in a background thread.
// Each task is run one after the other (on the same background thread) until all tasks have completed.
// The task chain will stop at the first task that fails.
taskChain.StopOnFailedTask = true;
success = taskChain.Run();
if (!success) {
    Debug.WriteLine(taskChain.LastErrorText);
    return;
}

// The application is now free to do anything else
// while the emails are being downloaded

// For this example, we'll simply sleep and periodically
// check to see if the taskchain if finished. 
while (taskChain.Finished != true) {

    // Sleep 100 ms.
    taskChain.SleepMs(100);

}

// A finished task chain could be one that was canceled, aborted, or truly finished.  

// If the task chain "completed", then it ran to completion.  A "completed" task will
// have a StatusInt equal to 7.   If the task finished, but was not completed, then it must've
// been aborted or canceled:
if (taskChain.StatusInt != 7) {
    Debug.WriteLine("Task did not complete.");
    Debug.WriteLine("task chain status: " + taskChain.Status);
    return;
}

Chilkat.Email email = new Chilkat.Email();

int numTasks = taskChain.NumTasks;
int taskIdx = 0;

while ((taskIdx < numTasks)) {

    task = taskChain.GetTask(taskIdx);

    // Load the email object with email downloaded by this task.
    success = email.LoadTaskResult(task);
    if (!success) {
        Debug.WriteLine("Failed to load email object for task.");
    }
    else {
        Debug.WriteLine(email.From + "; " + email.Subject);
    }

    taskIdx = taskIdx + 1;
}