(PowerShell) Async Task Chain

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

Chilkat .NET Downloads Chilkat .NET Assemblies

Add-Type -Path "C:\chilkat\ChilkatDotNet47-9.5.0-x64\ChilkatDotNet47.dll"

# All Chilkat classes can be unlocked at once at the beginning of a program
# by calling UnlockBundle.  It requires a Bundle unlock code.
$chilkatGlob = New-Object Chilkat.Global
$success = $chilkatGlob.UnlockBundle("Anything for 30-day trial.")
if ($success -ne $true) {
    $($chilkatGlob.LastErrorText)
    exit
}

$mailman = New-Object 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) {
    $($mailman.LastErrorText)
    exit
}

# Get the number of messages in the mailbox.
$numMessages = $mailman.GetMailboxCount()
if ($numMessages -eq 0) {
    $("No email messages in the POP3 mailbox.")
    exit
}

$taskChain = New-Object Chilkat.TaskChain

# Create async task objects to fetch each email message
# by its sequence number

for ($i = 1; $i -le $numMessages; $i++) {

    $task = $mailman.FetchByMsgnumAsync($i)
    if ($mailman.LastMethodSuccess -eq $false) {
        $($mailman.LastErrorText)
        exit
    }

    # Append each task to the task chain.
    $success = $taskChain.Append($task)
    if (!$success) {
        $($taskChain.LastErrorText)
        exit
    }

}

# 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) {
    $($taskChain.LastErrorText)
    exit
}

# 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 -ne $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 -ne 7) {
    $("Task did not complete.")
    $("task chain status: " + $taskChain.Status)
    exit
}

$email = New-Object Chilkat.Email

$numTasks = $taskChain.NumTasks
$taskIdx = 0

while (($taskIdx -lt $numTasks)) {

    $task = $taskChain.GetTask($taskIdx)

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

    $taskIdx = $taskIdx + 1
}