public override void OnApplyTemplate()
{
_expansionButton = this.GetTemplateChild("PART_ExpansionButton") as Arc;
if (_expansionButton != null)
{
_expansionButton.AddHandler(RadialMenuExtensionButton.MouseEnterEvent, new MouseEventHandler(this.OnMouseEnter));
_expansionButton.AddHandler(RadialMenuExtensionButton.MouseLeaveEvent, new MouseEventHandler(this.OnMouseLeave));
_expansionButton.AddHandler(RadialMenuExtensionButton.MouseLeftButtonUpEvent, new MouseButtonEventHandler(this.OnMouseLeftButtonUp));
}
}