using timer to change images in content page, working ok locally but showing error CS1061on server

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI.HtmlControls;
using System.Timers;

namespace WebApplication1
{
    public partial class WebForm3 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

            if (!IsPostBack)
            {
                addimages2();
            }
        }



        private void addimages2()
        {
            Random rand = new Random();
            int i = rand.Next(1, 4);
            Image1.ImageUrl = "~/pics/" + i.ToString() + ".jpg";
        }

        protected void Timer1_Tick(object sender, EventArgs e)
        {
            addimages2();
        }






    }
}

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

                <ContentTemplate>
                 <asp:Image ID="Image1" runat="server" Width="200px" Height="121px" />
                    <asp:Timer ID="Timer1" runat="server" Interval="1000" ontick="Timer1_Tick">
                    </asp:Timer>
                </ContentTemplate>

                </asp:UpdatePanel>