webforms - updatepanel refresh whole page in asp.net -

i use updatepanel in page this. when run app when click on button that's refresh of page. do'nt know can solve error. use treeview in other page when error treeview icon dont show. please me.

<asp:scriptmanager id="scriptmanager1" runat="server"> </asp:scriptmanager>      <asp:updatepanel id="updpanl" runat="server" rendermode="block" updatemode="conditional" >     <contenttemplate>    <asp:label id="label1" runat="server" text="label"></asp:label>         <asp:button id="button1" runat="server" onclick="button1_click" text="button" />     </contenttemplate>     </asp:updatepanel> 

try

<asp:scriptmanager id="scriptmanager1" runat="server"></asp:scriptmanager>  <asp:updatepanel id="updpanl"  childrenastriggers="true" runat="server" rendermode="block" updatemode="conditional" > <triggers>            <asp:asyncpostbacktrigger controlid="button1" eventname="click" />     </triggers>       <contenttemplate>    <asp:label id="label1" runat="server" text="label"></asp:label>         <asp:button id="button1" runat="server" onclick="button1_click" text="button" />     </contenttemplate>     </asp:updatepanel>  protected void button1_click(object sender, eventargs e)  {        updpanl.update(); }