in WhackAMole.UWPClient/SynchronizedObservableCollection.cs [616:637]
public void Insert(int index, T item)
{
_itemsLocker.EnterWriteLock();
try
{
CheckReentrancy();
if (index < 0 || index > _items.Count)
{
throw new ArgumentOutOfRangeException();
}
_items.Insert(index, item);
}
finally
{
_itemsLocker.ExitWriteLock();
}
OnNotifyItemAdded(item, index);
}