事件在.NET页面循环中没有及早触发

I have a Page (form) that has many UserControls on it, and I'm trying to have a single button to save everything. The UserControls are actually nested, so I wanted to somehow signal to each UC that it should save itself, instead of somehow wrapping everything into one event or having a single event trigger a cascade of save events.I have a Page (form) that has many UserControls