Forcing WPF to create the items in an ItemsControl

Question

I want to verify that the items in my ListBox are displayed correctly in the UI. I figured one way to do this is to go through all of the children of the

Answer 1

I think I figured out how to do this. The problem was that the generated items were not added to the visual tree. After some searching, the best I could come up with is to call some protected methods of the VirtualizingStackPanel in the ListBox. While this isn't ideal, since it's only for testing I think I'm going to have to live with it.

This is what worked for me:

VirtualizingStackPanel itemsPanel = null;
FrameworkElementFactory factory = control.ItemsPanel.VisualTree;
if(null != factory)
{
    // This method traverses the visual tree, searching for a control of
    // the specified type and name.
    itemsPanel = FindNamedDescendantOfType(control,
        factory.Type, null) as VirtualizingStackPanel;
}

List generatedItems = new List();
IItemContainerGenerator generator = this.ItemsListBox.ItemContainerGenerator;
GeneratorPosition pos = generator.GeneratorPositionFromIndex(-1);
using(generator.StartAt(pos, GeneratorDirection.Forward))
{
    bool isNewlyRealized;
    for(int i = 0; i < this.ItemsListBox.Items.Count; i++)
    {
        isNewlyRealized = false;
        UIElement cntr = generator.GenerateNext(out isNewlyRealized) as UIElement;
        if(isNewlyRealized)
        {
            if(i >= itemsPanel.Children.Count)
            {
                itemsPanel.GetType().InvokeMember("AddInternalChild",
                    BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.InvokeMember,
                    Type.DefaultBinder, itemsPanel,
                    new object[] { cntr });
            }
            else
            {
                itemsPanel.GetType().InvokeMember("InsertInternalChild",
                    BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.InvokeMember,
                    Type.DefaultBinder, itemsPanel,
                    new object[] { i, cntr });
            }

            generator.PrepareItemContainer(cntr);
        }

        string itemText = GetControlText(cntr);
        generatedItems.Add(itemText);
    }
}