update panel(ajax):

<%@ Page Title="Address Master" Language="C#" MasterPageFile="~/AdminZone/AdminMasterPage.master"
    AutoEventWireup="true" CodeFile="AddressMaster.aspx.cs" Inherits="AdminZone_AddressMaster" %>
<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="asp" %>
<asp:Content ID="Content1" ContentPlaceHolderID="head" runat="Server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="Server">
    <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>
                <div style="max-height: 420px; overflow: auto;">
                    <asp:UpdatePanel ID="updatePanelAddress" runat="server">
                        <ContentTemplate>
                            <table width="100%" cellpadding="0" cellspacing="5">
                                <tr>
                                    <td class="caption">
                                        Auto Id
                                    </td>
                                    <td class="captionSplitter">
                                        :
                                    </td>
                                    <td>
                                        <asp:Label ID="lblAutoId" runat="server" Text="Auto Generated"></asp:Label>
                                    </td>
                                </tr>
                                <tr>
                                    <td>
                                        Address Type
                                    </td>
                                    <td>
                                        :
                                    </td>
                                    <td>
                                        <asp:DropDownList ID="ddlAddressType" class="caption" runat="server" CssClass="caption"
                                            OnSelectedIndexChanged="ddlAddressType_SelectedIndexChanged" AutoPostBack="True">
                                        </asp:DropDownList>
                                        <asp:RequiredFieldValidator SetFocusOnError="true" ID="RequiredFieldValidator1" Display="Static"
                                            ValidationGroup="AddressValidationGroup" runat="server" ControlToValidate="ddlAddressType"
                                            ForeColor="Red" InitialValue="0" Text="*"></asp:RequiredFieldValidator>
                                    </td>
                                </tr>
                                <tr id="trAddressTitle" runat="server">
                                    <td>
                                        Address Title
                                    </td>
                                    <td>
                                        :
                                    </td>
                                    <td>
                                        <asp:TextBox ID="txtAddressTitle" CssClass="largeText" runat="server"></asp:TextBox>
                                    </td>
                                </tr>
                                <tr>
                                    <td>
                                        Building Name
                                    </td>
                                    <td>
                                        :
                                    </td>
                                    <td>
                                        <asp:TextBox ID="txtBuildingName" CssClass="largeText" runat="server"></asp:TextBox>
                                    </td>
                                </tr>
                                <tr>
                                    <td>
                                        House Number
                                    </td>
                                    <td>
                                        :
                                    </td>
                                    <td>
                                        <asp:TextBox ID="txtHouseNumber" CssClass="smallText" runat="server"></asp:TextBox>
                                    </td>
                                </tr>
                                <tr>
                                    <td>
                                        Plot Number
                                    </td>
                                    <td>
                                        :
                                    </td>
                                    <td>
                                        <asp:TextBox ID="txtPlotNumber" CssClass="smallText" runat="server"></asp:TextBox>
                                    </td>
                                </tr>
                                <tr>
                                    <td>
                                        Street
                                    </td>
                                    <td>
                                        :
                                    </td>
                                    <td>
                                        <asp:TextBox ID="txtStreet" runat="server" CssClass="largeText"></asp:TextBox>
                                    </td>
                                </tr>
                                <tr>
                                    <td>
                                        LandMark1
                                    </td>
                                    <td>
                                        :
                                    </td>
                                    <td>
                                        <asp:TextBox ID="txtLandMark1" runat="server" CssClass="largeText"></asp:TextBox>
                                    </td>
                                </tr>
                                <tr>
                                    <td>
                                        LandMark2
                                    </td>
                                    <td>
                                        :
                                    </td>
                                    <td>
                                        <asp:TextBox ID="txtLandMark2" runat="server" CssClass="largeText"></asp:TextBox>
                                    </td>
                                </tr>
                                <tr>
                                    <td colspan="3">
                                        Approach Detail
                                    </td>
                                </tr>
                                <tr>
                                    <td colspan="3">
                                        <asp:TextBox ID="txtApproachDetail" TextMode="MultiLine" runat="server"></asp:TextBox>
                                    </td>
                                </tr>
                                <tr>
                                    <td>
                                        Country
                                    </td>
                                    <td>
                                        :
                                    </td>
                                    <td>
                                        <asp:DropDownList ID="ddlCountry" class="caption" runat="server" AutoPostBack="True"
                                            CssClass="caption" OnSelectedIndexChanged="ddlCountry_SelectedIndexChanged">
                                        </asp:DropDownList>
                                        <asp:RequiredFieldValidator SetFocusOnError="true" ID="RequiredFieldValidator7" Display="Static"
                                            ValidationGroup="AddressValidationGroup" runat="server" ControlToValidate="ddlCountry"
                                            ForeColor="Red" InitialValue="0" Text="*"></asp:RequiredFieldValidator>
                                    </td>
                                </tr>
                                <tr>
                                    <td>
                                        State
                                    </td>
                                    <td>
                                        :
                                    </td>
                                    <td>
                                        <asp:DropDownList ID="ddlState" class="caption" runat="server" OnSelectedIndexChanged="ddlState_SelectedIndexChanged"
                                            AutoPostBack="True" CssClass="caption">
                                        </asp:DropDownList>
                                        <asp:RequiredFieldValidator SetFocusOnError="true" ID="RequiredFieldValidator6" Display="Static"
                                            ValidationGroup="AddressValidationGroup" runat="server" ControlToValidate="ddlState"
                                            ForeColor="Red" InitialValue="0" Text="*"></asp:RequiredFieldValidator>
                                    </td>
                                </tr>
                                <tr>
                                    <td>
                                        District
                                    </td>
                                    <td>
                                        :
                                    </td>
                                    <td>
                                        <asp:DropDownList ID="ddlDistrict" class="caption" runat="server" AutoPostBack="True"
                                            CssClass="caption" OnSelectedIndexChanged="ddlDistrict_SelectedIndexChanged">
                                        </asp:DropDownList>
                                        <asp:RequiredFieldValidator SetFocusOnError="true" ID="RequiredFieldValidator5" Display="Static"
                                            ValidationGroup="AddressValidationGroup" runat="server" ControlToValidate="ddlDistrict"
                                            ForeColor="Red" InitialValue="0" Text="*"></asp:RequiredFieldValidator>
                                    </td>
                                </tr>
                                <tr>
                                    <td>
                                        City
                                    </td>
                                    <td>
                                        :
                                    </td>
                                    <td>
                                        <asp:DropDownList ID="ddlCity" class="caption" runat="server" OnSelectedIndexChanged="ddlCity_SelectedIndexChanged"
                                            AutoPostBack="True" CssClass="caption">
                                        </asp:DropDownList>
                                        <asp:RequiredFieldValidator SetFocusOnError="true" ID="RequiredFieldValidator4" Display="Static"
                                            ValidationGroup="AddressValidationGroup" runat="server" ControlToValidate="ddlCity"
                                            ForeColor="Red" InitialValue="0" Text="*"></asp:RequiredFieldValidator>
                                    </td>
                                </tr>
                                <tr>
                                    <td>
                                        Area
                                    </td>
                                    <td>
                                        :
                                    </td>
                                    <td>
                                        <asp:DropDownList ID="ddlArea" class="caption" runat="server" OnSelectedIndexChanged="ddlArea_SelectedIndexChanged"
                                            AutoPostBack="True" CssClass="caption">
                                        </asp:DropDownList>
                                        <asp:RequiredFieldValidator SetFocusOnError="true" ID="RequiredFieldValidator3" Display="Static"
                                            ValidationGroup="AddressValidationGroup" runat="server" ControlToValidate="ddlArea"
                                            ForeColor="Red" InitialValue="0" Text="*"></asp:RequiredFieldValidator>
                                    </td>
                                </tr>
                                 </table>
                        </ContentTemplate>
                    </asp:UpdatePanel>
                </div>

</asp:Content>