Question

I need in wpf app check messages on server. I have own method which load messages on server-LoadRp().

I would like to create some kind of listener which would check, every 3 seconds whether on the server are not new messages.

I call method for loading messages on dispatcher timer tick event, it is suitable? Any another solution. It’s possible call timer in another thread in wpf?

Code is here:

    public MessangerWindow(PokecCommands pokecCmd)
    {
        InitializeComponent();

        PokecCmd = pokecCmd;

        _friendsData = PokecCmd.LoadFriends();
        friendsListBox.DataContext = _friendsData;

        _dispatcherTimer = new DispatcherTimer();
        _dispatcherTimer.Tick+=new EventHandler(DispatcherTimer_Tick);
        _dispatcherTimer.Interval = new TimeSpan(0,0,3);
        _dispatcherTimer.Start();
    }

    private void DispatcherTimer_Tick(object sender, EventArgs eventArgs)
    {
        try
        {

            //try load new message from sever
            RP message = PokecCmd.LoadRp();

            //arived message
            if (message != null)
            {
                //exist window
                if (_chatWindows.ContainsKey(message.Nick))
                {
                    _chatWindows[message.Nick].Show();
                }
                {
                    //create new Window
                    var chatWindow = new ChatWindow(PokecCmd, message);
                    _chatWindows.Add(message.Nick, chatWindow);
                    chatWindow.Show();
                }
            }
        }
        catch (Exception ex)
        {
            //MessageBox.Show(ex.Message);
        }  
    }

What is suitable to use:

• Dispatcher with no background threads
• Dispatcher with background threads
• Multiple Threads

Answer 1

If you are ok with locking up your UI for the time it takes to check on the server, using a DispatcherTimer the way you are doing it will work fine.

If checking for new messages could take more than a few milliseconds and you want your UI to be responsive while it checks, you should use multiple threads. In that case, once the new data had arrived you would use Dispatcher.Invoke to display it.

Your code in the thread that checks for messages might look like this:

//try load new message from sever 
RP message = PokecCmd.LoadRp(); 

//arived message 
if( message != null )
    Dispatcher.Invoke(DispatcherPriority.Send, new Action(() =>
        { 
            //exist window 
            if (_chatWindows.ContainsKey(message.Nick)) 
            { 
                _chatWindows[message.Nick].Show(); 
            } 
            { 
                //create new Window 
                var chatWindow = new ChatWindow(PokecCmd, message); 
                _chatWindows.Add(message.Nick, chatWindow); 
                chatWindow.Show(); 
            } 
        }
 );