问JQuery自动完成IE8 (Web服务ASMX)

EN

<asp:Content ID="Content1" ContentPlaceHolderID="head" runat="server">
<script type="text/javascript">
    $(document).ready(function () {
        $('#txtAutoFill').autocomplete({
            minLength: 2,
            source: function (request, response) {
                $.ajax({
                    url: 'UserList.asmx/GetAutoCompleteData',
                    method: 'post',
                    contentType: 'application/json;charset=utf-8',
                    //data: JSON.stringify({ username: request.username }),
                    data: request.username,
                    dataType: "json",
                    success: function (data) {
                        response(data.d);
                    },
                    error: function (XMLHttpRequest, textStatus, errorThrown) {
                        alert(textStatus);
                    }
                });
            }
        });
    });
</script>

<asp:Content ID="Content2" ContentPlaceHolderID="mainContentPH" runat="server">
    <h1 id="h01"></h1>
    <asp:TextBox ID="txtAutoFill" runat="server" CssClass="form-control"></asp:TextBox>

</asp:Content>