How do I access the children of an ItemsControl?

To identify ItemsControl's databound child controls (like a ToggleButton), you can use this:

for (int i = 0; i < yourItemsControl.Items.Count; i++)
{

    ContentPresenter c = (ContentPresenter)yourItemsControl.ItemContainerGenerator.ContainerFromItem(yourItemsControl.Items[i]);
    ToggleButton tb = c.ContentTemplate.FindName("btnYourButtonName", c) as ToggleButton;

    if (tb.IsChecked.Value)
    {
        //do stuff

    }
}

A solution similar to Seb's but probably with better performance :

for(int i = 0; i < itemsControl.Items.Count; i++)
{
    UIElement uiElement =
        (UIElement)itemsControl.ItemContainerGenerator.ContainerFromIndex(i);
}

See if this helps you out:

foreach(var item in itemsControl.Items)
{
    UIElement uiElement =
        (UIElement)itemsControl.ItemContainerGenerator.ContainerFromItem(item);
}

There is a difference between logical items in a control and an UIElement.