(.NET Core C#) Mark IMAP Email as Read/Unread (Seen/Unseen)

Demonstrates how to mark emails as read or unread.

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// This example assumes the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

Chilkat.Imap imap = new Chilkat.Imap();

// Connect to an IMAP server.
// Use TLS
imap.Ssl = true;
imap.Port = 993;
bool success = imap.Connect("imap.someMailServer.com");
if (success != true) {
    Debug.WriteLine(imap.LastErrorText);
    return;
}

// Login
success = imap.Login("myLogin","myPassword");
if (success != true) {
    Debug.WriteLine(imap.LastErrorText);
    return;
}

// Select an IMAP mailbox
success = imap.SelectMailbox("Inbox");
if (success != true) {
    Debug.WriteLine(imap.LastErrorText);
    return;
}

// Set PeekMode so that downloaded messages are not
// automatically marked as seen.
imap.PeekMode = true;

// The NumMessages property contains the number of messages 
// in the currently selected mailbox.
int numMsgs = imap.NumMessages;
if (numMsgs == 0) {
    return;
}

int i;
for (i = 1; i <= numMsgs; i++) {
    // Download each email by sequence number (not UID)
    Chilkat.Email email = null;
    email = imap.FetchSingle(i,false);
    if (imap.LastMethodSuccess == false) {
        Debug.WriteLine(imap.LastErrorText);
        return;
    }

    // If desired, mark the email as SEEN.  There are two
    // ways to do it:

    // 1) Set the flag directly by using the sequence number
    // Indicate that we are passing a sequence number and
    // not a UID:
    bool bIsUid = false;
    // Set the SEEN flag = 1 to mark the email as SEEN,
    // or set it to 0 to mark it as not-seen.
    success = imap.SetFlag(i,bIsUid,"SEEN",1);
    if (success != true) {
        Debug.WriteLine(imap.LastErrorText);
        return;
    }

    // 2) Alternatively, we can use the email object.
    // When an email is downloaded from the IMAP server
    // Chilkat will add a "ckx-imap-uid" header to the email.
    // This makes it possible to know the UID associated with
    // the email.  (This is not the sequence number, which may change
    // from session to session, but the UID which does not change.
    // The SetMailFlag method is identical to SetFlag, except
    // it gets the UID from the ckx-imap-uid header.
    // For example:
    success = imap.SetMailFlag(email,"SEEN",1);
    if (success != true) {
        Debug.WriteLine(imap.LastErrorText);
        return;
    }

}

// Disconnect from the IMAP server.
success = imap.Disconnect();