你设置的ItemsSource的那一刻，项目变为只读。你必须选择你要使用哪一个。你不能混搭在这里。因此，设置的ItemsSource之前，调用Items.Clear（）

The moment you set ItemsSource, Items becomes read only. You will have to pick which one you want to use. You can't mix and match here. So before setting ItemsSource, call Items.Clear()