https://learn.microsoft.com/en-us/dotnet/api/system.windows.controls.itemscontrol.onitemssourcechanged?view=netframework-4.8.1&viewFallbackFrom=windowsdesktop-10.0&redirectedfrom=MSDN
ItemsControl.OnItemsSourceChanged(IEnumerable, IEnumerable) Method (System.Windows.Controls) |...
Called when the ItemsSource property changes.
ienumerablemethodsystemwindowscontrols