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 // Derived from BindableBase Class which implements InotifyPropertyChanged
 public class SecondLevelViewModel : BindableBase
 {
 // constructor
 public SecondLevelViewModel()
 {
 // relevant instantiations
 ThirdLevels.ListChanged += ThirdLevels_ListChanged;
 //foreach (ThirdLevelViewModel thirdLevel in ThirdLevels)
 //{
 // thirdLevel.PropertyChanged += thirdLevel_PropertyChanged;
 //}
 }
 // ListChanged Event Handler
 private static void ThirdLevels_ListChanged(object? sender, ListChangedEventArgs e)
 {
 ArgumentNullException.ThrowIfNull(sender);
 BindingList<ThirdLevelViewModel> thirds = (BindingList<ThirdLevelViewModel>)sender!;
 // The example shows only the processing of the "ItemChanged" change type.
 // The rest of the values ​​are given only to show what types of changes there are.
 // If they do not need to be processed, they can be deleted.
 switch (e.ListChangedType)
 {
 case ListChangedType.ItemChanged:
 // Handling change of the ThirdLevelViewModel property
 {
 // We process only the next element.
 // Its change will cause ListChanged for it and
 // the next item will be processed in it.
 // And so on down the chain to the end of the collection.
 if (e.NewIndex < thirds.Count - 1)
 {
 ThirdLevelViewModel current = thirds[e.NewIndex];
 ThirdLevelViewModel next = thirds[e.NewIndex + 1];
 next.Duration = current.Duration + TimeSpan.FromSeconds(1);
 }
 }
 break;
 case ListChangedType.Reset:
 break;
 case ListChangedType.ItemAdded:
 break;
 case ListChangedType.ItemDeleted:
 break;
 case ListChangedType.ItemMoved:
 break;
 case ListChangedType.PropertyDescriptorAdded:
 break;
 case ListChangedType.PropertyDescriptorDeleted:
 break;
 case ListChangedType.PropertyDescriptorChanged:
 break;
 default:
 break;
 }
 }
 // properties
 public BindingList<ThirdLevelViewModel> ThirdLevels { get; } = new();
 }

 // Derived from BindableBase Class which implements InotifyPropertyChanged
 public class SecondLevelViewModel : BindableBase
 {
 // constructor
 public SecondLevelViewModel()
 {
 // relevant instantiations
 ThirdLevels.ListChanged += ThirdLevels_ListChanged;
 //foreach (ThirdLevelViewModel thirdLevel in ThirdLevels)
 //{
 // thirdLevel.PropertyChanged += thirdLevel_PropertyChanged;
 //}
 }
 // ListChanged Event Handler
 private static void ThirdLevels_ListChanged(object? sender, ListChangedEventArgs e)
 {
 ArgumentNullException.ThrowIfNull(sender);
 BindingList<ThirdLevelViewModel> thirds = (BindingList<ThirdLevelViewModel>)sender!;
 // The example shows only the processing of the "ItemChanged" change type.
 // The rest of the values ​​are given only to show what types of changes there are.
 // If they do not need to be processed, they can be deleted.
 switch (e.ListChangedType)
 {
 case ListChangedType.ItemChanged:
 // Handling change of the ThirdLevelViewModel property
 {
 // We process only the next element.
 // Its change will cause ListChanged for it and
 // the next item will be processed in it.
 // And so on down the chain to the end of the collection.
 if (e.NewIndex < thirds.Count - 1)
 {
 ThirdLevelViewModel current = thirds[e.NewIndex];
 ThirdLevelViewModel next = thirds[e.NewIndex + 1];
 switch (e.PropertyDescriptor?.Name)
 {
 case nameof(ThirdLevelViewModel.Duration):
 next.Duration = current.Duration + TimeSpan.FromSeconds(1);
 break;
 case nameof(ThirdLevelViewModel.StartTime):
 next.StartTime = current.StartTime.AddMinutes(1);
 break;
 default:
 break;
 }
 }
 }
 break;
 case ListChangedType.Reset:
 break;
 case ListChangedType.ItemAdded:
 break;
 case ListChangedType.ItemDeleted:
 break;
 case ListChangedType.ItemMoved:
 break;
 case ListChangedType.PropertyDescriptorAdded:
 break;
 case ListChangedType.PropertyDescriptorDeleted:
 break;
 case ListChangedType.PropertyDescriptorChanged:
 break;
 default:
 break;
 }
 }
 // properties
 public BindingList<ThirdLevelViewModel> ThirdLevels { get; } = new();
 }