How to disable background when jQuery Modal Dialog is opened with modal is false

Hi Aashish682,

I have created a sample which full fill your requirement

HTML

<div>
    <div>
        <input type="button" id="btnadd" value="Add Branch" name="btnadd" style="float: right" />
        <asp:Button ID="add" runat="server" Text="ADD" Style="display: none" OnClick="btninsert_Click">
        </asp:Button>
        <div id="disableBackGround" class="ui-widget-overlay" style="display: none; z-index: 1001;">
        </div>
    </div>
    <div id="modal_dialog" style="display: none">
        <div class="tab_container">
            <div id="tab2" class="tab_content">
                <table cellspacing="0">
                    <tbody>
                        <tr>
                            <td>
                                <b>Branch:</b>
                                <br />
                                <br />
                                BranchId: &nbsp; &nbsp;&nbsp; &nbsp;&nbsp;
                                <asp:TextBox ID="txtBranchId" runat="server" />
                                <br />
                                <br />
                                BranchName: &nbsp;
                                <asp:TextBox ID="txtBranchName" runat="server" />
                                <br />
                                <asp:Label ID="lbl_status" runat="server" ForeColor="Green" CssClass="red"></asp:Label>
                            </td>
                        </tr>
                    </tbody>
                </table>
            </div>
            <!-- end of #tab1 -->
        </div>
        <!-- ID -->
    </div>
    <div>
        <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
        <script type="text/javascript" src="http://cdnjs.cloudflare.com/ajax/libs/json2/20130526/json2.min.js"></script>
        <script src="http://ajax.aspnetcdn.com/ajax/jquery.ui/1.8.9/jquery-ui.js" type="text/javascript"></script>
        <link href="http://ajax.aspnetcdn.com/ajax/jquery.ui/1.8.9/themes/blitzer/jquery-ui.css"
            rel="stylesheet" type="text/css" />
        <script type="text/javascript">
            $(function () {
                $("#modal_dialog").dialog({
                    title: "Manage Branch",
                    autoOpen: false,
                    width: 300,
                    height: 350,
                    open: function () {
                        $('#disableBackGround').attr('style', 'display:block');
                    },
                    buttons: {
                        ADD: function () {
                            $('#<%=add.ClientID %>').click();
                        },
                        Close: function () {
                            $('#disableBackGround').attr('style', 'display:none');
                            $(this).dialog('close');
                        }
                    }
                });
                $("[id*=btnadd]").on("click", function () {
                    $("#modal_dialog").dialog('open');
                    return false;
                });
            });
        </script>
    </div>
</div>

C#

protected void btninsert_Click(object sender, EventArgs e)
{
    ClientScript.RegisterStartupScript(Page.GetType(), "key", "alert('Button Clicked')", true);
}

ScreenShot