asp.net - UpdatePanel sometimes refreshing entire page -

even though using update panel, entire page refreshed, , can't figure out why.

(edited take account jason p's answer.)

masterpage code:

<form runat="server" id="form1">         <asp:scriptmanager id="scriptmanager1" runat="server" enablepartialrendering="true" />          <h1>title</h1>          <asp:updatepanel id="updatepanel1" runat="server" updatemode="conditional" childrenastriggers="true">             <contenttemplate>                 <ul class="letterlinks">                     <asp:repeater runat="server" id="letter_repeater">                       <itemtemplate>                           <li id='<%#eval("letter")%>'>                                <asp:linkbutton runat="server" id="updatelink"  text="my text"                              commandname="bookletter" commandargument='<%#eval("letter")%>' oncommand="loadbooktitles"/>                            </li>                     </itemtemplate>                    </asp:repeater>                 </ul>                 <ul class="booklist">                     <asp:repeater runat="server" id="title_repeater">                         <itemtemplate>                             <li><a href='<%#eval("url")%>'><%#eval("title")%></a></li>                         </itemtemplate>                     </asp:repeater>                 </ul>             </contenttemplate>             </asp:updatepanel>          </form> 

code behind:

public partial class mybooks : system.web.ui.masterpage {     private getallbookinfo setmyinfo = new getallbookinfo();     private datatable alltitleinfo = new datatable();      protected void page_load(object sender, eventargs e)     {         list<string> letterswithbooks = new list<string>();          datatable letterlinks = new datatable();          // letters have books         letterswithbooks = setmyinfo.letterswithbooks();          // properties abc links         letterlinks = getletterlinkproperties(letterswithbooks);          // bind abc link data abc repeater         letter_repeater.datasource = letterlinks;         letter_repeater.databind();          alltitleinfo = setmyinfo.getbooktitles(letterswithbooks[0]);          // bind title info data title repeater          title_repeater.datasource = alltitleinfo;         title_repeater.databind();     }      private datatable getletterlinkproperties(list<string> letters)     {         datatable letterlinks = new datatable();         letterlinks.columns.add("letter", typeof(string));         letterlinks.columns.add("class", typeof(string));         letterlinks.columns.add("enabled", typeof(bool));          (char c = 'a'; c <= 'z'; c++)         {             if (letters.any(letter => letter == c.tostring()))             {                 letterlinks.rows.add(c, "hasguides", true);             }             else             {                 letterlinks.rows.add(c, "noguides", false);             }         }         return letterlinks;      protected void loadbooktitles(object sender, eventargs e)     {         linkbutton letterlink = (linkbutton)sender;          alltitleinfo = setmyinfo.getbooktitles(letterlink.commandargument string);          // bind title info data title repeater          title_repeater.datasource = alltitleinfo;         title_repeater.databind();     } } 

not sure if entire problem, <triggers> element should on same level <contenttemplate> element, not child:

<asp:updatepanel>     <triggers>         ...     <triggers>     <contenttemplate>         ...     <contenttemplate> </asp:updatepanel> 

also, believe in case, repeater should trigger, not linkbutton. try removing oncommand event linkbutton , adding repeater, , changing updatepanel's trigger.