获取控件中应用的模版的内部的控件，使用LoadContent()方法获取模版跟节点

treeview获取内部控件元素

Button btnAdd = ((tvks.HeaderTemplate as DataTemplate).LoadContent() as StackPanel).Children[2] as Button;

listbox获取子元素控件（针对数据绑定）

ListBoxItem container = lbAnm.ItemContainerGenerator.ContainerFromItem(lbAnm.Items[i]) as ListBoxItem;