Ajax in ASP.net
Ajax allows for only one section of the webpage to be reloaded during an event
Ajax extensions > Script manager >must be in content
update panel >content template ( must be in update panel)
Example
<asp:Content ID=”Content2″ ContentPlaceHolderID=”ContentPlaceHolder1″ Runat=”Server”>
<h2>Donation Form</h2>
Please fill out the following form
<asp:ScriptManager ID=”ScriptManager1″ runat=”server”>
</asp:ScriptManager>
<asp:RadioButtonList ID=”RadioButtonList1″ runat=”server” AutoPostBack=”True”
onselectedindexchanged=”RadioButtonList1_SelectedIndexChanged”>
<asp:ListItem>yes</asp:ListItem>
<asp:ListItem>no</asp:ListItem>
</asp:RadioButtonList>
<asp:UpdatePanel ID=”UpdatePanel1″ runat=”server”>
<ContentTemplate>
<asp:Panel ID=”Panel1″ runat=”server”>
[form elements here]
</asp:Panel>
</ContentTemplate>
</asp:UpdatePanel>
</asp:Content>
in design view, enable AutoPostBack for radio button list.