HandyControl/Net35/HandyControl_Net35/Interactivity/AttachableCollection!1.cs

using System;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Globalization;
using System.Windows;

namespace HandyControl.Interactivity
{
    public abstract class AttachableCollection<T> : FreezableCollection<T>, IAttachedObject
        where T : DependencyObject, IAttachedObject
    {
        private DependencyObject _associatedObject;
        private Collection<T> _snapshot;

        internal AttachableCollection()
        {
            INotifyCollectionChanged changed = this;
            changed.CollectionChanged += OnCollectionChanged;
            _snapshot = new Collection<T>();
        }

        public DependencyObject AssociatedObject
        {
            get
            {
                ReadPreamble();
                return _associatedObject;
            }
        }

        DependencyObject IAttachedObject.AssociatedObject => AssociatedObject;

        public void Attach(DependencyObject dependencyObject)
        {
            if (Equals(dependencyObject, AssociatedObject))
                return;
            if (AssociatedObject != null)
                throw new InvalidOperationException();
            if (Interaction.ShouldRunInDesignMode || !(bool) GetValue(DesignerProperties.IsInDesignModeProperty))
            {
                WritePreamble();
                _associatedObject = dependencyObject;
                WritePostscript();
            }
            OnAttached();
        }

        public void Detach()
        {
            OnDetaching();
            WritePreamble();
            _associatedObject = null;
            WritePostscript();
        }

        protected abstract void OnAttached();

        protected abstract void OnDetaching();

        internal abstract void ItemAdded(T item);

        internal abstract void ItemRemoved(T item);

        private void VerifyAdd(T item)
        {
            if (item == null) throw new ArgumentNullException(nameof(item));
            if (_snapshot.Contains(item))
                throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture,
                    ExceptionStringTable.DuplicateItemInCollectionExceptionMessage, new object[]
                    {
                        typeof(T).Name,
                        GetType().Name
                    }));
        }

        private void OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
        {
            switch (e.Action)
            {
                case NotifyCollectionChangedAction.Add:
                    var enumerator1 = e.NewItems.GetEnumerator();
                    try
                    {
                        while (enumerator1.MoveNext())
                        {
                            var current = (T) enumerator1.Current;
                            try
                            {
                                VerifyAdd(current);
                                ItemAdded(current);
                            }
                            finally
                            {
                                _snapshot.Insert(IndexOf(current), current);
                            }
                        }
                        break;
                    }
                    finally
                    {
                        if (enumerator1 is IDisposable disposable)
                            disposable.Dispose();
                    }
                case NotifyCollectionChangedAction.Remove:
                    var enumerator2 = e.OldItems.GetEnumerator();
                    try
                    {
                        while (enumerator2.MoveNext())
                        {
                            var current = (T) enumerator2.Current;
                            ItemRemoved(current);
                            _snapshot.Remove(current);
                        }
                        break;
                    }
                    finally
                    {
                        if (enumerator2 is IDisposable disposable)
                            disposable.Dispose();
                    }
                case NotifyCollectionChangedAction.Replace:
                    foreach (T oldItem in e.OldItems)
                    {
                        ItemRemoved(oldItem);
                        _snapshot.Remove(oldItem);
                    }
                    var enumerator3 = e.NewItems.GetEnumerator();
                    try
                    {
                        while (enumerator3.MoveNext())
                        {
                            var current = (T) enumerator3.Current;
                            try
                            {
                                VerifyAdd(current);
                                ItemAdded(current);
                            }
                            finally
                            {
                                _snapshot.Insert(IndexOf(current), current);
                            }
                        }
                        break;
                    }
                    finally
                    {
                        if (enumerator3 is IDisposable disposable)
                            disposable.Dispose();
                    }
                case NotifyCollectionChangedAction.Reset:
                    foreach (var obj in _snapshot)
                        ItemRemoved(obj);
                    _snapshot = new Collection<T>();
                    using (var enumerator4 = GetEnumerator())
                    {
                        while (enumerator4.MoveNext())
                        {
                            var current = enumerator4.Current;
                            VerifyAdd(current);
                            ItemAdded(current);
                        }
                        break;
                    }
            }
        }
    }
}