Binding dropdownlist to dropdownlist to detailsview ASP.NET C# -

i'm trying bind dropdownlist detailsview control in page result of second dropdownlist depends on first one. bind single dropdownlist detailsview if add dropdownlist result depends on first 1 details view wont show unless refresh page.

so there way post result of detailsview automatically if second dropdown selected? i'm studying this couldnt it.

here's sample code

<%@ page title="" language="c#" masterpagefile="~/site1.master" autoeventwireup="true" codebehind="search.aspx.cs" inherits="librarysystem.member.search" %> <asp:content id="content1" contentplaceholderid="head" runat="server"> </asp:content> <asp:content id="content2" contentplaceholderid="contentplaceholder1" runat="server">     <h3>         search</h3>     <p>         choose category         <asp:dropdownlist id="dropdownlist1" runat="server" autopostback="true"              datasourceid="categorydatasource" datatextfield="name"              datavaluefield="categoryid">         </asp:dropdownlist>         <asp:sqldatasource id="categorydatasource" runat="server"              connectionstring="<%$ connectionstrings:librarysystemconnectionstring %>"              selectcommand="select categoryid, name dbo.tblcategory">         </asp:sqldatasource>     </p>     <p>         choose title         <asp:dropdownlist id="dropdownlist2" runat="server" autopostback="true"              datasourceid="bookdatasource" datatextfield="booktitle" datavaluefield="bookid">         </asp:dropdownlist>         <asp:sqldatasource id="bookdatasource" runat="server"              connectionstring="<%$ connectionstrings:librarysystemconnectionstring %>"               selectcommand="select [categoryid], [booktitle], [bookid] [tblbooks] ([categoryid] = @categoryid)">             <selectparameters>                 <asp:controlparameter controlid="dropdownlist1" name="categoryid"                      propertyname="selectedvalue" type="int32" />             </selectparameters>         </asp:sqldatasource>     </p>     <p>         <asp:detailsview id="detailsview1" runat="server" autogeneraterows="false"              cellpadding="4" datakeynames="bookid" datasourceid="bookdetailsdatasource"              forecolor="#333333" gridlines="none">             <footerstyle backcolor="#507cd1" font-bold="true" forecolor="white" />             <commandrowstyle backcolor="#d1ddf1" font-bold="true" />             <rowstyle backcolor="#eff3fb" />             <fieldheaderstyle backcolor="#dee8f5" font-bold="true" />             <pagerstyle backcolor="#2461bf" forecolor="white" horizontalalign="center" />             <fields>                 <asp:boundfield datafield="bookid" headertext="id/isbn" readonly="true"                      sortexpression="bookid" />                 <asp:boundfield datafield="booktitle" headertext="title"                      sortexpression="booktitle" />                 <asp:boundfield datafield="lastname" headertext="author"                      sortexpression="lastname" />                 <asp:boundfield datafield="firstname" headertext=""                      sortexpression="firstname" />                 <asp:boundfield datafield="description" headertext="description"                      sortexpression="description" />                 <asp:boundfield datafield="name" headertext="category" sortexpression="name" />                 <asp:boundfield datafield="dateadded" headertext="date added"                      sortexpression="dateadded" />                 <asp:boundfield datafield="quantity" headertext="no. of copies"                      sortexpression="quantity" />                 <asp:boundfield datafield="employeeid" headertext="reserved by"                      sortexpression="employeeid" />                 <asp:boundfield datafield="reservedate" headertext="reserved date"                      sortexpression="reservedate" />                 <asp:boundfield datafield="statusname" headertext="status"                      sortexpression="statusname" />             </fields>             <headerstyle backcolor="#507cd1" font-bold="true" forecolor="white" />             <editrowstyle backcolor="#2461bf" />             <alternatingrowstyle backcolor="white" />         </asp:detailsview> 

any appreciated ;)

thanks in advance

you have put dependent dropdown datasource in parent template field. like...

 <asp:templatefield headertext="category">       <insertitemtemplate>         <asp:dropdownlist id="dropdownlist1" runat="server" autopostback="true" datasourceid="categorydatasource"                         datatextfield="name" datavaluefield="categoryid">                     </asp:dropdownlist>                     <asp:sqldatasource id="categorydatasource" runat="server" connectionstring="<%$ connectionstrings:librarysystemconnectionstring %>"                         selectcommand="select categoryid, name dbo.tblcategory"></asp:sqldatasource>                     <asp:sqldatasource id="bookdatasource" runat="server" connectionstring="<%$ connectionstrings:librarysystemconnectionstring %>"                         selectcommand="select [categoryid], [booktitle], [bookid] [tblbooks] ([categoryid] = @categoryid)">                         <selectparameters>                             <asp:controlparameter controlid="dropdownlist1" name="categoryid" propertyname="selectedvalue"                                 type="int32" />                         </selectparameters>                     </asp:sqldatasource>                 </insertitemtemplate>             </asp:templatefield>       <asp:templatefield headertext="title">                 <insertitemtemplate>                     <asp:dropdownlist id="dropdownlist2" runat="server" autopostback="true" datasourceid="bookdatasource"                         datatextfield="booktitle" datavaluefield="bookid">                     </asp:dropdownlist>                 </insertitemtemplate>             </asp:templatefield>