Structure
The structure of the RadPanelBar (Accordion) control is as follows:
The panel bar consists of a hierarchy of items. The items on one level are exposed when the parent item on the previous level is expanded. Each item is represented by a RadPanelItem instance.
At the top level are the root items. These items are always visible. They are available using the Items property of the panel bar (RadPanelBar.Items).
Each root item may have, nested within it, a set of child items. Children of the root items are considered level 1 items. They are available using the Items property of the root item (RadPanelItem.Items)
Child items may have, nested within them, their own sets of child items. Children of level 1 items are considered level 2 items; children of level 2 items are considered level 3 items; and so on.
One item in the panel bar can be designated as the Selected item. This is the last item that the user clicks, and has a distinct appearance from the other items at its level.
If the items are created at design time, the hierarchy is reflected in the ASP.NET declaration of the panel bar:
<telerik:RadPanelBar RenderMode="Lightweight" id="RadPanelBar1" runat="server" skin="Outlook">
<Items>
<telerik:RadPanelItem runat="server" Text="Mail">
<Items>
<telerik:RadPanelItem runat="server" Text="In Box" />
<telerik:RadPanelItem runat="server" Text="Deleted Items" />
<telerik:RadPanelItem runat="server" Text="Sent Items" />
</Items>
</telerik:RadPanelItem>
<telerik:RadPanelItem runat="server" Text="Calendar">
<Items>
<telerik:RadPanelItem runat="server">
<ItemTemplate>
<telerik:RadCalendar RenderMode="Lightweight" ID="RadCalendar1" runat="server" Skin="Outlook" />
</ItemTemplate>
</telerik:RadPanelItem>
</Items>
</telerik:RadPanelItem>
<telerik:RadPanelItem runat="server" Text="Notes">
<Items>
<telerik:RadPanelItem runat="server" Text="My Notes" />
<telerik:RadPanelItem runat="server" Text="Shared Notes" />
<telerik:RadPanelItem runat="server" IsSeparator="True" Text="<hr>" />
<telerik:RadPanelItem runat="server" Text="Archive" />
</Items>
</telerik:RadPanelItem>
</Items>
</telerik:RadPanelBar>