Verify AutoComplete Selected

I'm trying to prevent users from submitting a form without selecting something from my autocomplete. I don't want free text in my searchbox.

So far I can't get my code to work. what can I do to prevent

 $(document).ready(function () {
            $("#<%=txtSearch.ClientID%>").autocomplete("Search.ashx", {
                 extraParams: { "type": function () { return $("input:radio[name='toggle']:checked").val(); } },
                 width: 200,
                 formatItem: function (data, i, n, value) {
                     return "<img style = 'width:50px;height:50px' src='Images/doctypes/" + value.split(",")[1] + ".png'/> " + value.split(",")[0];
                 },
                 formatResult: function (data, value) {
                     return value.split(",")[0] + " # " + value.split(",")[2]
                 },
                 select: function (e, ui) {
                     alert(ui.item.value);
                 }
                 



            });

            $("#<%=txtSearch.ClientID%>").result(function (event, data, formatted) {
                if (data) {
                    $("#<%=hfSelected.ClientID%>").val("1");
                    $("#<%=tester.ClientID%>").html("Done");
                    //auto-complete matched

                }
                else {
                    $("#<%=hfSelected.ClientID%>").val("0");
                    $("#<%=tester.ClientID%>").html("Not Done");
                    //there was no match
                }
            });

            $("#<%=txtSearch.ClientID%>").blur(function () {
                $("#<%=txtSearch.ClientID%>").search(); //trigger result() on blur, even if autocomplete wasn't used
       
            });


         });

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