jQuery自动完成不在ASP.Net MVC4中显示数据

我有以下代码在jquery中生成自动完成

    <script type="text/javascript">
    $(function () {
        var url = '@Url.Action("GetDoctorByName", "Home")';
        var userName = $.trim($("#UserName").val());        
        $("#UserName").autocomplete({            
            source: function (request, response) {                
                //$("#UserName").keypress(function () {                        
                //if ($.trim(userName) != '') {
                $.ajax({
                    url: url,                    
                    datatype: "application/json; charset=utf-8",
                    type: "POST",
                    data: { userName: userName },                    
                    success: function (result) {
                        response($.map(result.resources, function (item) {    
                            var availableTags = [
                                        "ActionScript",
                                        "AppleScript",
                                        "Asp",
                                        "BASIC",
                                        "C",
                                        "C++",
                                        "Clojure",
                                        "COBOL",
                                        "ColdFusion",
                                        "Erlang",
                                        "Fortran",
                                        "Groovy",
                                        "Haskell",
                                        "Java",
                                        "JavaScript",
                                        "Lisp",
                                        "Perl",
                                        "PHP",
                                        "Python",
                                        "Ruby",
                                        "Scala",
                                        "Scheme"
                            ];
                        }));
                        if ($.trim(userName) == '') {                                                        
                        }                        
                    }                    
                });
            },
            minLength: 1
            }
            //}
            });
        //}        
        });

</script>

任何人都可以帮我