如何在不覆盖现有样式的情况下向WPF自定义控件添加触发器?

I am creating a simple custom control extending from toggle button that allows the user to specify checked and unchecked content directly in XAML. It works well but it is based on a trigger, and I don't know how to define the trigger except in a style. If I define the style, then I lose anything set outside of the custom control.I am creating a simple custom control extending