ASP.NET / C＃：DropDownList在服务器控件中没有触发的SelectedIndexChanged

I'm creating a server control that basically binds two dropdown lists, one for country and one for state, and updates the state dropdown on the country's selectedindexchanged event. However, it's not posting back. Any ideas why? Bonus points for wrapping them in an UpdatePanel (having rendering issues; maybe because I don't have a Page to reference?)I'm creating a server control that basically bi