How to programatically expand all expanders in window

Question

I've got a window with some expanders in it. When you open a expander there is some information inside it.

What i need to do is to open all expanders with one button so everything inside them becomes visible. When everything is visible i want to print the full page.

This is my code for expanding all expanders now:

public static IEnumerable<T> FindVisualChildren<T>(DependencyObject depObj) where T : DependencyObject
{
    if (depObj != null)
    {
        for (int i = 0; i < VisualTreeHelper.GetChildrenCount(depObj); i++)
        {
            DependencyObject child = VisualTreeHelper.GetChild(depObj, i);
            if (child != null && child is T)
            {
                yield return (T)child;
            }

            foreach (T childOfChild in FindVisualChildren<T>(child))
            {
                yield return childOfChild;
            }
        }
    }
}

The lines i use to iterate through my controls:

foreach (Expander exp in FindVisualChildren<Expander>(printpage))
{
    exp.IsExpanded = true;
}

Now to the point:

The code above works in most cases. The only problem i have is that sometimes there are some expanders WITHIN expanders. The parent expanders do expand when the above code executes, The child expanders however remain unexpanded.

I hope someone can teach me how to expand those child expanders too.

EDIT
I forgot to mention that the child-expanders are not direct childs of the main expanders..
They are children of children of children of the main expanders.

My controll-tree goes something like this:

-Stackpanel
---List item
-----Grid
-------Expander (Main expanders)
---------Grid
-----------Textblock
-------------Expander

So i need to expand all expanders in this tree.

Answer 1

Okay, I found my anwser in this post

The anwser on this question is what I used to solve my problem.

Here's the function I used:

public static List<T> GetLogicalChildCollection<T>(object parent) where T : DependencyObject
{
    List<T> logicalCollection = new List<T>();
    GetLogicalChildCollection(parent as DependencyObject, logicalCollection);
    return logicalCollection;
}

private static void GetLogicalChildCollection<T>(DependencyObject parent, List<T> logicalCollection) where T : DependencyObject
{
    IEnumerable children = LogicalTreeHelper.GetChildren(parent);
    foreach (object child in children)
    {
        if (child is DependencyObject)
        {
            DependencyObject depChild = child as DependencyObject;
            if (child is T)
            {
                logicalCollection.Add(child as T);
            }
            GetLogicalChildCollection(depChild, logicalCollection);
        }
    }
}

In my code I used these lines to append what I needed to my expanders:

List<Expander> exp = GetLogicalChildCollection<Expander>(printpage.StackPanelPrinting);

foreach (Expander exp in expander)
{
    exp.IsExpanded = true;
    exp.FontWeight = FontWeights.Bold;
    exp.Background = Brushes.LightBlue;
}