This answer quotes ChatGPT
In WPF, calling grid.child.clear() will only Clear the child elements in the Grid control, not the page's cache. If you use a Grid control as a parent form and nest child forms within it, clearing the children of the Grid removes them from the parent form, but does not affect the child form itself.
If you want to clear the page cache completely, try using the Frame control to clear the page cache by navigating to a blank page, such as:
// 清空页面缓存 frame.Navigate(new Page());
If you still want to use Grid controls and need to clear the page cache in a parent-child form nesting, you can try manually clearing the controls and data in the child form to clear the page cache.