Question

I’m writing a filter that will pick out items. I have a list of Objects. The objects contain a number, name and some other irrelevant items. At the moment, the list contains 200 items. When typing in a textbox, i’m looking if the string matches a part of the number/name of the objects in the list. If so, add them to the listbox. Here’s the code for my textbox textchanged event :

private void txtTelnumber_TextChanged(object sender, TextChangedEventArgs e)
    {
        lstOverview.Items.Clear();
        string data = "";
        foreach (ucTelListItem telList in _allUsers)
        {
            data = telList.User.H323 + telList.user.E164;
            if (data.Contains(txtTelnumber.Text))
                lstOverview.Items.Add(telList);
        }
    }

I sometimes see a little delay when entering a character, especially when i go from 4 records to 200 records (so when i had a filter and 4 records matched, and i backspace and the whole list appears again).
My list is a list of usercontrols, cause I found it takes less time to load the usercontrols from a list, then to have to initialize a new usercontrol each time.

Can I do something about the code, or is it just adding the usercontrol the listbox that causes the small delay (small delay = <1 sec)?

Thanks in advance.

Edit
I’ve edited post, it’s wpf. And putting items in a list and setting the itemssource isn’t solving the problem.

Answer 1

I’d suggest you two techniques to be used in concert:

1. Before clearing and adding item to the ListBox invoke the BeginUpdate() method, and invoke its EndUpdate() when you finish adding items. These methods are specifically there for avoiding performance loss during a massive insertion of items.
2. Introduce a timer and make the filtering task start only after a specific amount of time has been elapsed after the last KeyUp event of the TextBox. In this way you augment the chance of not evaluating a filter that is not yet significant to the user.