// Works flawlessly
for (int i = 0; i < Root.Count; ++i)
{
    Console.WriteLine("Begin SectionLoop");
    for (int j = 0; j < Root[i].Count; ++j)
    {
        Console.WriteLine("Element: " + Root[i][j]);
        if (typeof(EntryElement) == Root[i][j].GetType())
        {
            if (((EntryElement)Root[i][j]).Entry != null && ((EntryElement)Root[i][j]).Entry.IsFirstResponder)
            {
                ((EntryElement)Root[i][j]).Entry.ResignFirstResponder();
            }
        }
    }
    Console.WriteLine("End SectionLoop");
}

// Does not even output "Begin SectionLoop", but dies with a SIGSEGV
foreach (Section section in Root)
{
    Console.WriteLine("Begin SectionLoop");
    foreach (Element entryElement in section)
    {
        Console.WriteLine("Element: " + entryElement);
        if (typeof(EntryElement) == entryElement.GetType())
        {
            if (((EntryElement)entryElement).Entry != null && ((EntryElement)entryElement).Entry.IsFirstResponder)
            {
                ((EntryElement)entryElement).Entry.ResignFirstResponder();
            }
        }
    }
    Console.WriteLine("End SectionLoop");
}