As far as I have been able to tell, this is not implemented, so I put together a handler that should work. This is preliminary (I have not gone all the way with implementation), but it might help others:

Normal 0 false false false EN-CA X-NONE X-NONE MicrosoftInternetExplorer4

function eventToChar(code) {

    if (code < 32 || // Shift codes, etc.

        (code > 32 && code < 41) || // Arrows, etc.

        (code >= 45 && code <= 46) || // Ins, Del

        (code >= 91 && code <= 93) || // Window keys, select key

        (code >= 112 && code <= 123) || // F1 - F12

        (code >= 144 && code <= 145) || // Num lock, scroll lock

        code >= 256)

        return null;

    else

        return String.fromCharCode(code);

}

function dropDownMatch(control, match) {

    if (control.get_enableCaseSensitivity()) {

        for (i = 0; i < control.get_items().getLength(); i++) {

            // if (items[i].get_text() == match || items[i].get_text().startsWith(match)) {

            if (control.get_items().getItem(i).get_text() == match || control.get_items().getItem(i).get_text().startsWith(match)) {

                return control.get_items().getItem(i);

            }

        }

    } else {

        for (i = 0; i < control.get_items().getLength(); i++) {

            if (control.get_items().getItem(i).get_text() == match.toLowerCase() || control.get_items().getItem(i).get_text().toLowerCase().startsWith(match.toLowerCase())) {

                return control.get_items().getItem(i);

            }

        }

    }

    return null;

}

function selectFirstDropDownMatch(control, match) {

    var matchedItem = dropDownMatch(control, match);

    if (matchedItem) {

        if (!control.behavior.get_visible() && !control.behavior.get_isAnimating()) {

            control.openDropDown();

        }

        control.__scrollToItem(matchedItem);

        control.set_activeItem(matchedItem);

        return true;

    } else

        return false;

}

function startClearMatchTimer(control) {

    clearTimeout(control._clearMatchTimerID);

    control._clearMatchTimerID = setTimeout(

        function() { clearMatchTimer(control); }, 1500);

}

function clearMatchTimer(control) {

    control._matchText = undefined;

}

function inputKeyUp(control, event) {

    var code = event.get_browserEvent().keyCode;

    var match = control._matchText;

    if (!match)

        match = "";

    if (code == 8) { // Backspace

        match = match.substring(0, match.length - 2);

        selectFirstDropDownMatch(control, match);

        control._matchText = match;

        startClearMatchTimer(control);

    } else {

        matchChar = eventToChar(code);

        if (matchChar) {

            match = match + matchChar;

            if (selectFirstDropDownMatch(control, match)) {

                control._matchText = match; // Only set if the match succeeded

                startClearMatchTimer(control);

            }

        }

    }

}

Assign it to <ClientEvents InputKeyUp="inputKeyUp" /> in the <ig:WebDropDown> to get the functionality. Uses the control's own case-sensitivity settings, and the 'search string' clears after a second and a half (the 1500) of not typing.

--=- Ritchie Annand