Jquery UI中对话框的空标题

我写了这个脚本，用户选中要删除的复选框信息，然后单击删除按钮，它用ajax删除信息。我的问题是，当我第一次删除时，一切都很好，但在第二次对话框的标题是空的。为什么？

我在显示对话框后使用此代码，因为我的标题是动态的：

$（"#ui-id-1"）.text（tittle）

<script src="../../Scripts/jquery-1.8.3.js"></script>
<script src="../../Scripts/jquery-ui-1.9.2.custom.js"></script>
    <script>
        $(function () {
            $(":checkbox").change(function () {
                var $this = $(this);
                if ($this.is(":checked")) {
                    $this.closest("tr").addClass("SlectedtRow");
                } else {
                    $this.closest("tr").removeClass("SlectedtRow");
                }
            })
            var tittle = '';
            var url = '';
            $("#dialog").dialog({
                autoOpen: false,
                width: 400,
                modal: true,
                resizable: false,
                buttons: [
                    {
                        text: "بلی",
                        click: function () {
                            Delete();
                            $(this).dialog("close");
                        }
                    },
                    {
                        text: "خیر",
                        click: function () {
                            $(this).dialog("close");
                        }
                    }
                ]
            });
            var IsActive
            // Link to open the dialog
            $(".insertBtn").click(function (event) {
                var IsSelected = false;
                var ModalText = "  آیا کاربر ";
                $('#userForm input:checked').each(function () {
                    ModalText += this.value + " - "
                    IsSelected = true;
                });
                if (IsSelected) {
                    document.getElementById('ErrorContent').style.display = "none";
                    ModalText = ModalText.slice(0, -2);
                    if (this.id == 'DeleteUser') {
                        ModalText += " حذف گردد  "
                        tittle = 'حذف کاربر'
                        url = '@Url.Action("DeleteUser", "UserManagement")';
                    }
                    else if (this.id == 'InActiveUser') {
                        ModalText += " غیر فعال گردد  "
                        tittle = 'تغییر فعالیت کاربر '
                        url = '@Url.Action("ChangeActiveStatus", "UserManagement")';
                    IsActive = false;
                }
                else if (this.id == 'ActiveUser') {
                    ModalText += "  فعال گردد  "
                    tittle = 'تغییر فعالیت کاربر '
                    url = '@Url.Action("ChangeActiveStatus", "UserManagement")';
                    IsActive = true;
                }
        $('#ModalMessgae').text(ModalText);

        $("#dialog").dialog("open");
        $("#ui-id-1").text(tittle);
        event.preventDefault();
    }        })
            function Delete() {
                var list = [];
                $('#userForm input:checked').each(function () {
                    list.push(this.id);
                });
                var parameters = {};
                if (url == '@Url.Action("DeleteUser", "UserManagement")') {
                parameters = JSON.stringify(list);
            }
            else {
                parameters = JSON.stringify({ "userId": list, "ISActive": IsActive });
            }
            $.ajax({
                url: url,
                type: 'POST',
                contentType: 'application/json; charset=utf-8',
                dataType: "html",
                traditional: true,
                data: parameters,
                success: function (data, textStatus, jqXHR) {
                    $('#updateAjax').html(data);
                },
                error: function (data) {
                    $('#updateAjax').html(data);
                }
            });   //end ajax
        }
        });
    </script>

html标记

@using Common.UsersManagement.Entities;
@model IEnumerable<VwUser>
@{
    Layout = "~/Views/Shared/Master.cshtml";
}
<form id="userForm">
    <div id="updateAjax">
        @if (string.IsNullOrWhiteSpace(ViewBag.MessageResult) == false)
        {
            <div class="@ViewBag.cssClass">
                @Html.Label(ViewBag.MessageResult as string)
            </div>
            <br />
        }
        <table class="table" cellspacing="0">
            @foreach (VwUser Item in Model)
            {   
                <tr class="@(Item.IsActive ? "tRow" : "Disable-tRow")">
                    <td class="tbody">
                        <input type="checkbox" id="@Item.Id" name="selected"  value="@Item.FullName"/></td>
                    <td class="tbody">@Item.FullName</td>
                    <td class="tbody">@Item.Post</td>
                    <td class="tbody">@Item.Education</td>
                </tr>
            }
        </table>
    </div>
    <br />
    <br />
@if (!Request.IsAjaxRequest())
{
    <div class="btnContainer">
        <a href="#" id="DeleteUser" class="insertBtn">delete  </a>
        <br />
        <br />
    </div>}