There are some other settings that can affect how the Accordion works.  I mentioned before that the Accordion only displays one AccordionItem in the control.  This is an adjustable setting controlled by the SelectionMode property.  This enumerated property controls whether only one entry can be expanded, zero entries can be expanded, or multiple entries can be expanded.  For instance, changing this value to the value ZeroOrOne will allow zero items to be selected (by clicking the selected accordion a second time).

Setting the ExpandDirection property changes the expander to expand up, down, left, or right, by changing the value (an enumerated property).  The SelectionSequence determines the actions the Accordion takes when selecting an item.  If Simultaneous is set, the Accordion shows and hides the AccordionItem at the same time; otherwise, the currently selected item is collapsed, followed by expanding the newly selected item.

The Accordion keeps track of which items are selected via SelectedItem, SelectedIndex, and SelectedIndices (in modes where multiple selections are allowed).  These properties can be read or set accordingly.