In this step, you will add a C1ExpanderExtender control to associate with the Panel to create the expanding text.
<cc1:C1ExpanderExtender ID="Panel1_C1ExpanderExtender" runat="server"
TargetControlID="Panel1">
</cc1:C1ExpanderExtender>
Now you can begin setting properties for the C1ExpanderExtender to format the expanding text.