Trying to use a jquery-ui combobox in asp.net webforms

Question

I'm trying to use the jqueryUI combobox into my asp.net 3.5 webforms application. I've added a dropdownlist and modified it style with jquery. The problem i got is when i try to execute the postback the dropdown normally does when it selected item it's changed. The combobox doesn't change it's value and I'm getting the error that _dopostback is not defined in my firebug error console. I've been reading about this here and in and in in the asp.net forums, and found some answers that told me that should give a try to the GetPostBackEventReference method, but still nothing has happened. Below is the code, thanks.

<script type="text/javascript">
    (function ($) {
        $.widget("ui.combobox", {
            _create: function () {
                var input,
                self = this,
                select = this.element.hide(),
                selected = select.children(":selected"),
                value = selected.val() ? selected.text() : "",
                wrapper = $("<span>")
                    .addClass("ui-combobox")
                    .insertAfter(select);

                input = $("<input>")
                .appendTo(wrapper)
                .val(value)
                .addClass("ui-state-default")
                .autocomplete({
                    delay: 0,
                    minLength: 0,
                    source: function (request, response) {
                        var matcher = new RegExp($.ui.autocomplete.escapeRegex(request.term), "i");
                        response(select.children("option").map(function () {
                            var text = $(this).text();
                            if (this.value && (!request.term || matcher.test(text)))
                                return {
                                    label: text.replace(
                                        new RegExp(
                                            "(?![^&;]+;)(?!<[^<>]*)(" +
                                            $.ui.autocomplete.escapeRegex(request.term) +
                                            ")(?![^<>]*>)(?![^&;]+;)", "gi"
                                        ), "<strong>$1</strong>"),
                                    value: text,
                                    option: this
                                };
                        }));
                    },
                    select: function (event, ui) {
                        ui.item.option.selected = true;
                        self._trigger("selected", event, {
                            item: ui.item.option
                        });
                        _doPostBack('<%= ddlModalities.UniqueID %>', "");
                    },
                    change: function (event, ui) {
                        if (!ui.item) {
                            var matcher = new RegExp("^" + $.ui.autocomplete.escapeRegex($(this).val()) + "$", "i"),
                                valid = false;
                            select.children("option").each(function () {
                                if ($(this).text().match(matcher)) {
                                    this.selected = valid = true;
                                    $(select).change();

                                    return false;
                                }
                            });
                            if (!valid) {
                                // remove invalid value, as it didn't match anything
                                $(this).val("");
                                select.val("");
                                input.data("autocomplete").term = "";
                                return false;
                            }
                        }
                    }
                })
                .addClass("ui-widget ui-widget-content ui-corner-left");

                input.data("autocomplete")._renderItem = function (ul, item) {
                    return $("<li></li>")
                    .data("item.autocomplete", item)
                    .append("<a>" + item.label + "</a>")
                    .appendTo(ul);
                };

                $("<a>")
                .attr("tabIndex", -1)
                .attr("title", "Show All Items")
                .appendTo(wrapper)
                .button({
                    icons: {
                        primary: "ui-icon-triangle-1-s"
                    },
                    text: false
                })
                .removeClass("ui-corner-all")
                .addClass("ui-corner-right ui-button-icon")
                .click(function () {
                    // close if already visible
                    if (input.autocomplete("widget").is(":visible")) {
                        input.autocomplete("close");
                        return;
                    }

                    // work around a bug (likely same cause as #5265)
                    $(this).blur();

                    // pass empty string as value to search for, displaying all results
                    input.autocomplete("search", "");
                    input.focus();
                });
            },

            destroy: function () {
                this.wrapper.remove();
                this.element.show();
                $.Widget.prototype.destroy.call(this);
            }
        });
    })(jQuery);

    $(function () {
        $("#<%=ddlModalities.ClientID %>").combobox();
    });
</script>

<div class="ui-widget">
    <asp:DropDownList runat="server" ID="ddlModalities" Width="150px" AutoPostBack="True"
                                DataSourceID="odsModalitiesNoWorklist" DataTextField="Ae" DataValueField="Id"
                                CssClass="ddlStandardWidth" OnDataBound="ddlModalities_DataBound" OnSelectedIndexChanged="ddlModalities_SelectedIndexChanged" />
                        </div>

Answer 1

It looks like you're calling "_doPostBack". However, the ASP.NET-generated function is "__doPostBack" - there are two "_" characters at the beginning, not just one. That could be the cause of your "function not defined" error.