How do you access the children of a WPF Canvas class?

How do you access the children of a WPF Canvas class?
It is a cool class and I like how you are able to add children.  But once they are there, how to you look at them for reading their state and content.  I know it is easy if you put the children in XAML.  But what if you have added children to the canvas dynamically at run time?