Umbraco-CMS/src/Umbraco.Core/Collections/EventClearingObservableCollection.cs

using System.Collections.ObjectModel;
using System.Collections.Specialized;
using Umbraco.Cms.Core.Models;

namespace Umbraco.Cms.Core.Collections;

/// <summary>
///     Allows clearing all event handlers
/// </summary>
/// <typeparam name="TValue"></typeparam>
public class EventClearingObservableCollection<TValue> : ObservableCollection<TValue>, INotifyCollectionChanged, IDeepCloneable
{
    // need to explicitly implement with event accessor syntax in order to override in order to to clear
    // c# events are weird, they do not behave the same way as other c# things that are 'virtual',
    // a good article is here: https://medium.com/@unicorn_dev/virtual-events-in-c-something-went-wrong-c6f6f5fbe252
    // and https://stackoverflow.com/questions/2268065/c-sharp-language-design-explicit-interface-implementation-of-an-event
    private NotifyCollectionChangedEventHandler? _changed;

    public EventClearingObservableCollection()
    {
    }

    public EventClearingObservableCollection(List<TValue> list)
        : base(list)
    {
    }

    public EventClearingObservableCollection(IEnumerable<TValue> collection)
        : base(collection)
    {
    }

    event NotifyCollectionChangedEventHandler? INotifyCollectionChanged.CollectionChanged
    {
        add => _changed += value;
        remove => _changed -= value;
    }

    /// <summary>
    ///     Clears all event handlers for the <see cref="INotifyCollectionChanged.CollectionChanged" /> event.
    /// </summary>
    public void ClearCollectionChangedEvents() => _changed = null;

    public object DeepClone()
    {
        var clone = new EventClearingObservableCollection<TValue>();
        DeepCloneHelper.CloneListItems<EventClearingObservableCollection<TValue>, TValue>(this, clone);

        return clone;
    }
}