WPF DocumentViewer不会释放XPS文件

I am working on a WPF application that opens and displays XPS documents. When the application closes, the specification is the application should delete the opened XPS document for clean up. However, when opening a certain XPS document, the application throws an exception that the file is still in use when it tries to delete it. It is a little weird because it only happens when opening a particular XPS document and only when you have moved beyond the first page. I am working on a WPF application that opens an