When the AutoExpandAllItems property is set to true, the accordion control will automatically expand all its items when:
- the Accordion control is initialized
- the control's ItemsSource property is changed.
When a single item is changed in the data source, the item's child nodes are expanded.
When the ChildrenPath and DisplayMemberPath properties are specified, and the bound data items implement System.ComponentModel.INotifyPropertyChanged, the accordion items are expanded only when the items' properties specified within ChildrenPath and DisplayMemberPath are changed.