Default.aspx

<%@ Page Title="" Language="C#" MasterPageFile="~/MasterPage.master" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<asp:Content ID="Content1" ContentPlaceHolderID="head" runat="Server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="Server">
    <section id="mu-pricing">
        <div class="container">
            <div class="row">
                <div class="col-md-12">
                    <div class="mu-pricing-area">
                        <asp:ScriptManager ID="s1" runat="server"></asp:ScriptManager>

                        <asp:UpdatePanel ID="UpdatePanel1" runat="server">

                            <ContentTemplate>

                                <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
                                <asp:Button ID="Button1" runat="server" Text="Clear" OnClick="Button1_Click" />
                            </ContentTemplate>
                            <Triggers>
                                <asp:AsyncPostBackTrigger ControlID="Button1" EventName="Click" />
<asp:popupcontrolextender runat="server"></asp:popupcontrolextender>

                            </Triggers>
                        </asp:UpdatePanel>
                    </div>
                </div>
            </div>
        </div>
    </section>
</asp:Content>