Idle Method

Informs the server it can send unsolicited mailbox update information. Blocks execution until a command is sent on another thread. The Update event is raised as each update is received.

Syntax

Visual Basic (Declaration)
Visual Basic (Usage)
C#
Managed Extensions for C++
C++/CLI

Public Function Idle() As ImapResponse

Dim instance As Imap
Dim value As ImapResponse
 
value = instance.Idle()

public ImapResponse Idle()

public: ImapResponse* Idle();

public:
ImapResponse^ Idle();

Exceptions

Exception	Description
System.InvalidOperationException	A Mailbox is not selected.
System.NotSupportedException	Server does not support the IDLE command.

Remarks

RFC 2177 defines the IDLE command that indicates the client desires unsolicited updates for the selected mailbox. This method blocks until the user sends another command (on another thread). While blocking, the Update event is raised as each update is received.

For single-threaded applications, use Noop to poll for updates. For multi-threaded applications, call Idle() on a worker thread, where it will block until the client sends another command (on the UI thread or on a different worker thread).

Example

This example demonstrates use of the Idle method and the Update event.

/// <summary>
/// Used here as a stand-in for any collection that should be updated to reflect 
/// the current state of messages on the server, such as a ListView.Items collection.
/// </summary>
Dictionary<string, ImapMessage> independentImapMessageCollection = new Dictionary<string, ImapMessage>();

private void button1_Click(object sender, EventArgs e)
{
    //Set server and account info
    imap1.Session.RemoteEndPoint = new Dart.Mail.IPEndPoint(myServer, Imap.GetDefaultPort(imap1.Session));
    imap1.Session.Username = myUsername;
    imap1.Session.Password = myPassword;

    //Start a worker thread
    //This allows the function to execute without blocking the UI
    imap1.Start(listenForUpdates, null);
}

private void button2_Click(object sender, EventArgs e)
{
    //Set server and account info
    smtp1.Session.RemoteEndPoint = new Dart.Mail.IPEndPoint(mySmtpServer, Smtp.GetDefaultPort(smtp1.Session));
    smtp1.Session.Username = myUsername;
    smtp1.Session.Password = myPassword;

    //Send a message to trigger an exists update.
    smtp1.Send(myEmail, myEmail, "Test Message", "Test Message");
}

private void listenForUpdates(object state)
{
    //This function executes on a worker thread
    //Connect and log into the account
    imap1.Connect();
    imap1.Authenticate();

    //Set the current mailbox to INBOX
    imap1.SelectedMailbox = imap1.Mailboxes["INBOX"];

    //Retrieve all messages in the mailbox
    imap1.SelectedMailbox.Get();

    //Add the retrieved messages to the independent collection of ImapMessages
    foreach (ImapMessage message in imap1.SelectedMailbox.ToArray())
        independentImapMessageCollection.Add(message.Uid, message);

    //Initiate Idle to await new updates from server
    imap1.Idle();

    //Idle() returns once the client intiates communication with the server (on a different thread).
    System.Diagnostics.Debug.WriteLine("DONE IDLING");
}

private void imap1_Update(object sender, ImapUpdateEventArgs e)
{
    switch (e.Response.Operation)
    {
        case "EXPUNGE":
            //Remove message(s) from any independently implemented collection
            foreach (ImapMessage msg in e.Messages)
                independentImapMessageCollection.Remove(msg.Uid);
            break;

        case "EXISTS":
            //Retrieve the new messages on a worker thread
            imap1.Start(getMessages, e.Messages);
            break;
    }
}

/// <summary>
/// When the server informs the client of new messages, download the new messages (interrupts IDLE).
/// </summary>
void getMessages(object msgs)
{
    //Executes on a worker thread so UI messages are not interrupted.
    //Cast msgs back to ImapMessage array
    ImapMessage[] messages = msgs as ImapMessage[];

    //Retrieve the new messages from the server. This interrupts IDLE.
    imap1.SelectedMailbox.Get(messages, ImapMessageInfo.Message);

    //Update the independent collection
    foreach (ImapMessage message in messages)
        independentImapMessageCollection.Add(message.Uid, message);

    //Resume Idle to await new updates from server
    imap1.Idle();

    //Idle() returns once the client intiates communication with the server (on a different thread).
    System.Diagnostics.Debug.WriteLine("DONE IDLING");
}

Visual Basic

''' <summary>
''' Used here as a stand-in for any collection that should be updated to reflect 
''' the current state of messages on the server, such as a ListView.Items collection.
''' </summary>
Private independentImapMessageCollection As New Dictionary(Of String, ImapMessage)()

Private Sub button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles button1.Click
    'Set server and account info
    imap1.Session.RemoteEndPoint = New Dart.Mail.IPEndPoint(myServer, Imap.GetDefaultPort(imap1.Session))
    imap1.Session.Username = myUsername
    imap1.Session.Password = myPassword

    'Start a worker thread
    'This allows the function to execute without blocking the UI
    imap1.Start(AddressOf listenForUpdates, Nothing)
End Sub

Private Sub button2_Click(ByVal sender As Object, ByVal e As EventArgs) Handles button2.Click
    'Set server and account info
    smtp1.Session.RemoteEndPoint = New Dart.Mail.IPEndPoint(mySmtpServer, Smtp.GetDefaultPort(smtp1.Session))
    smtp1.Session.Username = myUsername
    smtp1.Session.Password = myPassword

    'Send a message to trigger an exists update.
    smtp1.Send(myEmail, myEmail, "Test Message", "Test Message")
End Sub

Private Sub listenForUpdates(ByVal state As Object)
    'This function executes on a worker thread
    'Connect and log into the account
    imap1.Connect()
    imap1.Authenticate()

    'Set the current mailbox to INBOX
    imap1.SelectedMailbox = imap1.Mailboxes("INBOX")

    'Retrieve all messages in the mailbox
    imap1.SelectedMailbox.Get()

    'Add the retrieved messages to the independent collection of ImapMessages
    For Each message As ImapMessage In imap1.SelectedMailbox.ToArray()
        independentImapMessageCollection.Add(message.Uid, message)
    Next message

    'Initiate Idle to await new updates from server
    imap1.Idle()

    'Idle() returns once the client intiates communication with the server (on a different thread).
    System.Diagnostics.Debug.WriteLine("DONE IDLING")
End Sub

Private Sub imap1_Update(ByVal sender As Object, ByVal e As ImapUpdateEventArgs) Handles imap1.Update
    Select Case e.Response.Operation
        Case "EXPUNGE"
            'Remove message(s) from any independently implemented collection
            For Each msg As ImapMessage In e.Messages
                independentImapMessageCollection.Remove(msg.Uid)
            Next msg

        Case "EXISTS"
            'Retrieve the new messages on a worker thread
            imap1.Start(AddressOf getMessages, e.Messages)
    End Select
End Sub

''' <summary>
''' When the server informs the client of new messages, download the new messages (interrupts IDLE).
''' </summary>
Private Sub getMessages(ByVal msgs As Object)
    'Executes on a worker thread so UI messages are not interrupted.
    'Cast msgs back to ImapMessage array
    Dim messages() As ImapMessage = TryCast(msgs, ImapMessage())

    'Retrieve the new messages from the server. This interrupts IDLE.
    imap1.SelectedMailbox.Get(messages, ImapMessageInfo.Message)

    'Update the independent collection
    For Each message As ImapMessage In messages
        independentImapMessageCollection.Add(message.Uid, message)
    Next message

    'Resume Idle to await new updates from server
    imap1.Idle()

    'Idle() returns once the client intiates communication with the server (on a different thread).
    System.Diagnostics.Debug.WriteLine("DONE IDLING")
End Sub

Reference

Imap Class
Imap Members