showing modalpopup using ajax ModalPopupExtender ID and javascript

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ASP.NET

hi,i have a button ,i want that when i click on that button the data should be saved in the database as well as at the same time a modal popup
should display the customerid .i have written the code as

<asp:button id="save1" runat="server" onclick="Button4_Click" style=""z-index:" mode="hold" xmlns:asp="#unknown" />           left: 740px; position: absolute; top: 304px" Text="save"/>

<asp:panel id="panel" runat="server" xmlns:asp="#unknown"></asp:panel>

                <ajaxtoolkit:modalpopupextender id="MPE" runat="server" targetcontrolid="save1" xmlns:ajaxtoolkit="#unknown">
                PopupControlID="panel" DropShadow="true"
                BackgroundCssClass="modalBackground/>
</ajaxtoolkit:modalpopupextender>

protected void Button4_Click(object sender, EventArgs e)
   {
       string id = TextBox1.Text;
       string name = TextBox2.Text;
       string cn = "Data Source=hcl;Initial Catalog=mydata;Integrated Security=True";
       SqlConnection con = new SqlConnection(cn);
       SqlCommand cmd = new SqlCommand("insert into customer values (@id,@name)", con);
       con.Open();
       cmd.CommandType = CommandType.Text;
       cmd.Parameters.Add("@id", id);
       cmd.Parameters.Add("@name",name);

       cmd.ExecuteNonQuery();

       con.Close();
       CUSTID.Text = id.ToString();
       MPE.Show();
}

but it is not happening.even if i comment the MPE.Show() line a popup
is coming.i m not understanding what is happening plz help i want code using ajax as well as normal javascript.