EO.Wpf Menu can expand a sub menu both on mouse over event and mouse click event. The default behavior is mouse click for the top level menu items and mouse over for sub menu items. You can change this behavior by changing TopLevelItemExpandOnClick and SubItemExpandOnClick.

When sub menus are triggered by mouse over event, the menu can appear "over sensitive" when user accidently moved mouse away from a sub menu or over another menu item for a short period of time, which would trigger a sub menu to expand or collapse by default. To avoid sub menu expands or collapses due to such short mouse movement, you can set the menu's ExpandDelay and CollapseDelay property.

By default, a sub menu closes when user clicks a menu item. You can set a MenuItem's StaysOpenOnClick to true to prevent the sub menu from closing when the menu item is clicked.