Shaan
here i changed the state based on the country ..
in javascript add this.. based on ur requirement..
<pre lang="xml"><asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:DropDownList ID="ddlcountry" runat="server" AutoPostBack="True"
onselectedindexchanged="ddlcountry_SelectedIndexChanged" >
</asp:DropDownList>
<br />
<br />
<br />
<asp:DropDownList ID="ddlstate" runat="server"
AutoPostBack="True" ></asp:DropDownList>
and in codebahind jst add bind the data for example in ddlcountry_SelectedIndexChanged event(i have used LINQ)
IEnumerable<State> res = db.States.Where(s => s.CountryId ==int .Parse (ddlcountry.SelectedValue));<br />
ddlstate.DataSource = sl;<br />
ddlstate.DataTextField = "StateName";<br />
ddlstate.DataValueField = "StateId";<br />
<br />
ddlstate.DataBind();<br />
<br />