BindingList vs ObservableCollection

internal static class SecurityUtils
{
    private static volatile ReflectionPermission _memberAccessPermission;
    private static volatile ReflectionPermission _restrictedMemberAccessPermission;

    private static ReflectionPermission memberAccessPermission =>
        _memberAccessPermission ??
        (_memberAccessPermission = new ReflectionPermission(ReflectionPermissionFlag.MemberAccess));

    private static ReflectionPermission restrictedMemberAccessPermission =>
        _restrictedMemberAccessPermission ??
        (_restrictedMemberAccessPermission =
            new ReflectionPermission(ReflectionPermissionFlag.RestrictedMemberAccess));

    private static void demandReflectionAccess(Type type)
    {
        try
        {
            memberAccessPermission.Demand();
        }
        catch (SecurityException)
        {
            demandGrantSet(type.Assembly);
        }
    }

    [SecuritySafeCritical]
    private static void demandGrantSet(Assembly assembly)
    {
        var permissionSet = assembly.PermissionSet;
        var accessPermission = restrictedMemberAccessPermission;
        permissionSet.AddPermission(accessPermission);
        permissionSet.Demand();
    }

    private static bool hasReflectionPermission(Type type)
    {
        try
        {
            demandReflectionAccess(type);
            return true;
        }
        catch (SecurityException)
        {
        }
        return false;
    }

    internal static object SecureCreateInstance(Type type)
    {
        return SecureCreateInstance(type, null, false);
    }

    internal static object SecureCreateInstance(Type type, object[] args, bool allowNonPublic)
    {
        if (type == null)
            throw new ArgumentNullException(nameof(type));
        var bindingAttr = BindingFlags.Instance | BindingFlags.Public | BindingFlags.CreateInstance;
        if (!type.IsVisible)
            demandReflectionAccess(type);
        else if (allowNonPublic && !hasReflectionPermission(type))
            allowNonPublic = false;
        if (allowNonPublic)
            bindingAttr |= BindingFlags.NonPublic;
        return Activator.CreateInstance(type, bindingAttr, null, args, null);
    }

    internal static object SecureCreateInstance(Type type, object[] args)
    {
        return SecureCreateInstance(type, args, false);
    }

    internal static object SecureConstructorInvoke(Type type, Type[] argTypes, object[] args, bool allowNonPublic)
    {
        return SecureConstructorInvoke(type, argTypes, args, allowNonPublic, BindingFlags.Default);
    }

    internal static object SecureConstructorInvoke(Type type, Type[] argTypes, object[] args, bool allowNonPublic,
        BindingFlags extraFlags)
    {
        if (type == null)
            throw new ArgumentNullException(nameof(type));
        if (!type.IsVisible)
            demandReflectionAccess(type);
        else if (allowNonPublic && !hasReflectionPermission(type))
            allowNonPublic = false;
        var bindingAttr = BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic | extraFlags;
        if (!allowNonPublic)
            bindingAttr &= ~BindingFlags.NonPublic;
        var constructor = type.GetConstructor(bindingAttr, null, argTypes, null);
        return constructor?.Invoke(args);
    }

    private static bool genericArgumentsAreVisible(MethodInfo method)
    {
        return !method.IsGenericMethod || method.GetGenericArguments().All(type => type.IsVisible);
    }

    internal static object FieldInfoGetValue(FieldInfo field, object target)
    {
        var declaringType = field.DeclaringType;
        if (declaringType == null)
        {
            if (!field.IsPublic)
                demandGrantSet(field.Module.Assembly);
        }
        else if (!declaringType.IsVisible || !field.IsPublic)
            demandReflectionAccess(declaringType);
        return field.GetValue(target);
    }

    internal static object MethodInfoInvoke(MethodInfo method, object target, object[] args)
    {
        var declaringType = method.DeclaringType;
        if (declaringType == null)
        {
            if (!method.IsPublic || !genericArgumentsAreVisible(method))
                demandGrantSet(method.Module.Assembly);
        }
        else if (!declaringType.IsVisible || !method.IsPublic || !genericArgumentsAreVisible(method))
            demandReflectionAccess(declaringType);
        return method.Invoke(target, args);
    }

    internal static object ConstructorInfoInvoke(ConstructorInfo ctor, object[] args)
    {
        var declaringType = ctor.DeclaringType;
        if (declaringType != null && (!declaringType.IsVisible || !ctor.IsPublic))
            demandReflectionAccess(declaringType);
        return ctor.Invoke(args);
    }

    internal static object ArrayCreateInstance(Type type, int length)
    {
        if (!type.IsVisible)
            demandReflectionAccess(type);
        return Array.CreateInstance(type, length);
    }
}

public class AdvancedCollection<T> : IList<T>,IList, IReadOnlyList<T>
{
    private readonly List<T> _innerList;
    private readonly Dictionary<T, List<int>> _reverseIndex;
    private readonly object _syncRoot=new object();

    public AdvancedCollection()
    {
        _innerList = new List<T>();
        _reverseIndex = new Dictionary<T, List<int>>();
    }

    public AdvancedCollection(IList<T> list):this()
    {
        _innerList.Clear();
        _innerList.AddRange(list);
        refreshIndexes();
    }

    private void refreshIndexes()
    {
        lock (_syncRoot)
        {
            _reverseIndex.Clear();
            for (var i = 0; i < _innerList.Count; i++)
            {
                var item = _innerList[i];
                List<int> indexes;
                if (!_reverseIndex.TryGetValue(item, out indexes))
                {
                    indexes = new List<int>();
                    _reverseIndex[item] = indexes;
                }
                indexes.Add(i);
            }
        }
    }

    public int IndexOf(T item)
    {
        List<int> indexes;
        if (!_reverseIndex.TryGetValue(item, out indexes)) return -1;
        return indexes.Count == 0 ? -1 : indexes[0];
    }

    public void Insert(int index, T item)
    {
        lock (_syncRoot)
        {
            var indexesList = Enumerable.Range(index, _innerList.Count - index)
                .Select(i => _reverseIndex[_innerList[i]])
                .Distinct();
            foreach (var indexes in indexesList)
            {
                for (var j = 0; j < indexes.Count; j++)
                {
                    if (indexes[j] >= index)
                    {
                        indexes[j]++;
                    }
                }
            }
            _innerList.Insert(index, item);
        }
    }

    public void RemoveAt(int index)
    {
        lock (_syncRoot)
        {
            var indexesList = Enumerable.Range(index, _innerList.Count - index)
                .Select(i => _reverseIndex[_innerList[i]])
                .Distinct();
            foreach (var indexes in indexesList)
            {
                for (var j = 0; j < indexes.Count; j++)
                {
                    var i = indexes[j];
                    if (i == index)
                    {
                        indexes.RemoveAt(j);
                        j--;
                        continue;
                    }
                    if (indexes[j] > index)
                    {
                        indexes[j]--;
                    }
                }
            }
            _innerList.RemoveAt(index);
        }
    }

    public T this[int index]
    {
        get { return _innerList[index]; }
        set
        {
            lock (_syncRoot)
            {
                var indexes = _reverseIndex[_innerList[index]];
                indexes.Remove(index);
                if (!_reverseIndex.TryGetValue(value, out indexes))
                {
                    indexes = new List<int>();
                    _reverseIndex[value] = indexes;
                }
                indexes.Add(index);
                indexes.Sort();
            }
        }
    }


    int IList.Add(object value)
    {
        return add((T) value);
    }

    bool IList.Contains(object value)
    {
        return ((IList<T>) this).Contains((T) value);
    }

    void IList.Clear()
    {
        lock (_syncRoot)
        {
            _innerList.Clear();
            _reverseIndex.Clear();
        }
    }

    int IList.IndexOf(object value)
    {
        return ((IList<T>) this).IndexOf((T) value);
    }

    void IList.Insert(int index, object value)
    {
        ((IList<T>)this).Insert(index, (T)value);
    }

    void IList.Remove(object value)
    {
        var index = ((IList) this).IndexOf(value);
        if (index < 0) return;
        ((IList) this).RemoveAt(index);
    }

    void IList.RemoveAt(int index)
    {
        ((IList<T>) this).RemoveAt(index);
    }

    object IList.this[int index]
    {
        get { return ((IList<T>)this)[index]; }
        set
        {
            var item = (T) value;
            ((IList<T>)this)[index] = item;
        }
    }

    bool IList.IsReadOnly => false;

    bool IList.IsFixedSize => false;

    void ICollection.CopyTo(Array array, int index)
    {
        ((IList)_innerList).CopyTo(array,index);
    }

    public int Count => _innerList.Count;

    object ICollection.SyncRoot => _syncRoot;

    bool ICollection.IsSynchronized => false;

    IEnumerator<T> IEnumerable<T>.GetEnumerator()
    {
        return _innerList.GetEnumerator();
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return ((IEnumerable<T>) this).GetEnumerator();
    }

    public void Add(T item)
    {
        add(item);
    }

    public void Clear()
    {
        ((IList) this).Clear();
    }

    bool ICollection<T>.Contains(T item)
    {
        lock (_syncRoot)
        {
            return _reverseIndex.ContainsKey(item);
        }
    }

    void ICollection<T>.CopyTo(T[] array, int arrayIndex)
    {
        lock (_syncRoot)
        {
            _innerList.CopyTo(array, arrayIndex);
        }
    }

    bool ICollection<T>.Remove(T item)
    {
        var index = ((IList<T>)this).IndexOf(item);
        if (index < 0) return false;
        ((IList<T>)this).RemoveAt(index);
        return true;
    }

    int ICollection<T>.Count => _innerList.Count;

    bool ICollection<T>.IsReadOnly => false;

    int IReadOnlyCollection<T>.Count => _innerList.Count;

    T IReadOnlyList<T>.this[int index] => ((IList<T>) this)[index];

    private int add(T item)
    {
        lock (_syncRoot)
        {
            var index = _innerList.Count;
            _innerList.Add(item);
            List<int> indexes;
            if (!_reverseIndex.TryGetValue(item, out indexes))
            {
                indexes = new List<int>();
                _reverseIndex[item] = indexes;
            }
            indexes.Add(index);
            return index;
        }
    }

    protected virtual void ClearItems()
    {
        ((IList<T>)this).Clear();
    }

    protected virtual void InsertItem(int index, T item)
    {
        ((IList<T>)this).Insert(index,item);
    }

    protected virtual void RemoveItem(int index)
    {
        ((IList<T>)this).RemoveAt(index);
    }

    protected virtual void SetItem(int index, T item)
    {
        this[index] = item;
    }
}

/// <summary>
///     Provides a generic collection that supports data binding.
/// </summary>
/// <typeparam name="T">The type of elements in the list.</typeparam>
[Serializable]
[HostProtection(SecurityAction.LinkDemand, SharedState = true)]
public class AdvancedBindingList<T> : AdvancedCollection<T>, IBindingList, ICancelAddNew, IRaiseItemChangedEvents,
    INotifyCollectionChanged
{
    private int _addNewPos = -1;
    private bool _allowEdit = true;
    private bool _allowNew = true;
    private bool _allowRemove = true;

    [NonSerialized] private PropertyDescriptorCollection _itemTypeProperties;

    [NonSerialized] private int _lastChangeIndex = -1;

    [NonSerialized] private AddingNewEventHandler _onAddingNew;

    [NonSerialized] private PropertyChangedEventHandler _propertyChangedEventHandler;

    private bool _raiseItemChangedEvents;
    private bool _raiseListChangedEvents = true;
    private bool _userSetAllowNew;

    /// <summary>
    ///     Initializes a new instance of the <see cref="T:System.ComponentModel.BindingList`1" /> class using default values.
    /// </summary>
    public AdvancedBindingList()
    {
        initialize();
    }

    /// <summary>
    ///     Initializes a new instance of the <see cref="T:System.ComponentModel.BindingList`1" /> class with the specified
    ///     list.
    /// </summary>
    /// <param name="list">
    ///     An <see cref="T:System.Collections.Generic.IList`1" /> of items to be contained in the
    ///     <see cref="T:System.ComponentModel.BindingList`1" />.
    /// </param>
    public AdvancedBindingList(IList<T> list)
        : base(list)
    {
        initialize();
    }

    private bool itemTypeHasDefaultConstructor
    {
        get
        {
            var type = typeof (T);
            return type.IsPrimitive ||
                    type.GetConstructor(BindingFlags.Instance | BindingFlags.Public | BindingFlags.CreateInstance,
                        null, new Type[0], null) != null;
        }
    }

    /// <summary>
    ///     Gets or sets a value indicating whether adding or removing items within the list raises
    ///     <see cref="E:System.ComponentModel.BindingList`1.ListChanged" /> events.
    /// </summary>
    /// <returns>
    ///     true if adding or removing items raises <see cref="E:System.ComponentModel.BindingList`1.ListChanged" /> events;
    ///     otherwise, false. The default is true.
    /// </returns>
    public bool RaiseListChangedEvents
    {
        get { return _raiseListChangedEvents; }
        set { _raiseListChangedEvents = value; }
    }

    private bool addingNewHandled
    {
        get
        {
            if (_onAddingNew != null)
                return (uint) _onAddingNew.GetInvocationList().Length > 0U;
            return false;
        }
    }

    /// <summary>
    ///     Gets or sets a value indicating whether you can add items to the list using the
    ///     <see cref="M:System.ComponentModel.BindingList`1.AddNew" /> method.
    /// </summary>
    /// <returns>
    ///     true if you can add items to the list with the <see cref="M:System.ComponentModel.BindingList`1.AddNew" /> method;
    ///     otherwise, false. The default depends on the underlying type contained in the list.
    /// </returns>
    public bool AllowNew
    {
        get
        {
            if (_userSetAllowNew || _allowNew)
                return _allowNew;
            return addingNewHandled;
        }
        set
        {
            var num1 = AllowNew ? 1 : 0;
            _userSetAllowNew = true;
            _allowNew = value;
            var num2 = value ? 1 : 0;
            if (num1 == num2)
                return;
            fireListReset();
        }
    }

    /// <summary>
    ///     Gets or sets a value indicating whether items in the list can be edited.
    /// </summary>
    /// <returns>
    ///     true if list items can be edited; otherwise, false. The default is true.
    /// </returns>
    public bool AllowEdit
    {
        get { return _allowEdit; }
        set
        {
            if (_allowEdit == value)
                return;
            _allowEdit = value;
            fireListReset();
        }
    }

    /// <summary>
    ///     Gets or sets a value indicating whether you can remove items from the collection.
    /// </summary>
    /// <returns>
    ///     true if you can remove items from the list with the
    ///     <see cref="M:System.ComponentModel.BindingList`1.RemoveItem(System.Int32)" /> method otherwise, false. The default
    ///     is true.
    /// </returns>
    public bool AllowRemove
    {
        get { return _allowRemove; }
        set
        {
            if (_allowRemove == value)
                return;
            _allowRemove = value;
            fireListReset();
        }
    }

    /// <summary>
    ///     Gets a value indicating whether <see cref="E:System.ComponentModel.BindingList`1.ListChanged" /> events are
    ///     enabled.
    /// </summary>
    /// <returns>
    ///     true if <see cref="E:System.ComponentModel.BindingList`1.ListChanged" /> events are supported; otherwise, false.
    ///     The default is true.
    /// </returns>
    protected virtual bool SupportsChangeNotificationCore => true;

    /// <summary>
    ///     Gets a value indicating whether the list supports searching.
    /// </summary>
    /// <returns>
    ///     true if the list supports searching; otherwise, false. The default is false.
    /// </returns>
    protected virtual bool SupportsSearchingCore => false;

    /// <summary>
    ///     Gets a value indicating whether the list supports sorting.
    /// </summary>
    /// <returns>
    ///     true if the list supports sorting; otherwise, false. The default is false.
    /// </returns>
    protected virtual bool SupportsSortingCore => false;

    /// <summary>
    ///     Gets a value indicating whether the list is sorted.
    /// </summary>
    /// <returns>
    ///     true if the list is sorted; otherwise, false. The default is false.
    /// </returns>
    protected virtual bool IsSortedCore => false;

    /// <summary>
    ///     Gets the property descriptor that is used for sorting the list if sorting is implemented in a derived class;
    ///     otherwise, returns null.
    /// </summary>
    /// <returns>
    ///     The <see cref="T:System.ComponentModel.PropertyDescriptor" /> used for sorting the list.
    /// </returns>
    protected virtual PropertyDescriptor SortPropertyCore => null;

    /// <summary>
    ///     Gets the direction the list is sorted.
    /// </summary>
    /// <returns>
    ///     One of the <see cref="T:System.ComponentModel.ListSortDirection" /> values. The default is
    ///     <see cref="F:System.ComponentModel.ListSortDirection.Ascending" />.
    /// </returns>
    protected virtual ListSortDirection SortDirectionCore => ListSortDirection.Ascending;

    bool IBindingList.AllowNew => AllowNew;

    bool IBindingList.AllowEdit => AllowEdit;

    bool IBindingList.AllowRemove => AllowRemove;

    bool IBindingList.SupportsChangeNotification => SupportsChangeNotificationCore;

    bool IBindingList.SupportsSearching => SupportsSearchingCore;

    bool IBindingList.SupportsSorting => SupportsSortingCore;

    bool IBindingList.IsSorted => IsSortedCore;

    PropertyDescriptor IBindingList.SortProperty => SortPropertyCore;

    ListSortDirection IBindingList.SortDirection => SortDirectionCore;

    /// <summary>
    ///     Occurs when the list or an item in the list changes.
    /// </summary>
    public event ListChangedEventHandler ListChanged;

    object IBindingList.AddNew()
    {
        var obj = AddNewCore();
        _addNewPos = obj != null ? ((IList<T>) this).IndexOf((T) obj) : -1;
        return obj;
    }

    void IBindingList.ApplySort(PropertyDescriptor prop, ListSortDirection direction)
    {
        ApplySortCore(prop, direction);
    }

    void IBindingList.RemoveSort()
    {
        RemoveSortCore();
    }

    int IBindingList.Find(PropertyDescriptor prop, object key)
    {
        return FindCore(prop, key);
    }

    void IBindingList.AddIndex(PropertyDescriptor prop)
    {
    }

    void IBindingList.RemoveIndex(PropertyDescriptor prop)
    {
    }

    /// <summary>
    ///     Discards a pending new item.
    /// </summary>
    /// <param name="itemIndex">The index of the of the new item to be added </param>
    public virtual void CancelNew(int itemIndex)
    {
        if (_addNewPos < 0 || _addNewPos != itemIndex)
            return;
        RemoveItem(_addNewPos);
        _addNewPos = -1;
    }

    /// <summary>
    ///     Commits a pending new item to the collection.
    /// </summary>
    /// <param name="itemIndex">The index of the new item to be added.</param>
    public virtual void EndNew(int itemIndex)
    {
        if (_addNewPos < 0 || _addNewPos != itemIndex)
            return;
        _addNewPos = -1;
    }

    public event NotifyCollectionChangedEventHandler CollectionChanged;

    bool IRaiseItemChangedEvents.RaisesItemChangedEvents => _raiseItemChangedEvents;

    private void fireListReset()
    {
        fireListChanged(ListChangedType.Reset, -1);
        CollectionChanged?.Invoke(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
    }

    /// <summary>
    ///     Occurs before an item is added to the list.
    /// </summary>
    public event AddingNewEventHandler AddingNew
    {
        add
        {
            var num1 = AllowNew ? 1 : 0;
            _onAddingNew = _onAddingNew + value;
            var num2 = AllowNew ? 1 : 0;
            if (num1 == num2)
                return;
            fireListReset();
        }
        remove
        {
            var num1 = AllowNew ? 1 : 0;
            // ReSharper disable once DelegateSubtraction
            _onAddingNew = _onAddingNew - value;
            var num2 = AllowNew ? 1 : 0;
            if (num1 == num2)
                return;
            fireListReset();
        }
    }

    private void initialize()
    {
        _allowNew = itemTypeHasDefaultConstructor;
        if (!typeof (INotifyPropertyChanged).IsAssignableFrom(typeof (T)))
            return;
        _raiseItemChangedEvents = true;
        foreach (var obj in this)
            hookPropertyChanged(obj);
    }

    /// <summary>
    ///     Raises the <see cref="E:System.ComponentModel.BindingList`1.AddingNew" /> event.
    /// </summary>
    /// <param name="e">An <see cref="T:System.ComponentModel.AddingNewEventArgs" /> that contains the event data. </param>
    protected virtual void OnAddingNew(AddingNewEventArgs e)
    {
        _onAddingNew?.Invoke(this, e);
    }

    private object fireAddingNew()
    {
        var e = new AddingNewEventArgs(null);
        OnAddingNew(e);
        return e.NewObject;
    }

    /// <summary>
    ///     Raises the <see cref="E:System.ComponentModel.BindingList`1.ListChanged" /> event.
    /// </summary>
    /// <param name="e">A <see cref="T:System.ComponentModel.ListChangedEventArgs" /> that contains the event data. </param>
    protected virtual void OnListChanged(ListChangedEventArgs e)
    {
        ListChanged?.Invoke(this, e);
    }

    /// <summary>
    ///     Raises a <see cref="E:System.ComponentModel.BindingList`1.ListChanged" /> event of type
    ///     <see cref="F:System.ComponentModel.ListChangedType.Reset" />.
    /// </summary>
    public void ResetBindings()
    {
        fireListReset();
    }

    /// <summary>
    ///     Raises a <see cref="E:System.ComponentModel.BindingList`1.ListChanged" /> event of type
    ///     <see cref="F:System.ComponentModel.ListChangedType.ItemChanged" /> for the item at the specified position.
    /// </summary>
    /// <param name="position">A zero-based index of the item to be reset.</param>
    public void ResetItem(int position)
    {
        fireListChanged(ListChangedType.ItemChanged, position);
        CollectionChanged?.Invoke(this,
            new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Replace, this[position],position));
    }

    private void fireListChanged(ListChangedType type, int index)
    {
        if (!_raiseListChangedEvents)
            return;
        OnListChanged(new ListChangedEventArgs(type, index));
    }

    /// <summary>
    ///     Removes all elements from the collection.
    /// </summary>
    protected override void ClearItems()
    {
        EndNew(_addNewPos);
        if (_raiseItemChangedEvents)
        {
            foreach (var obj in this)
                unhookPropertyChanged(obj);
        }
        base.ClearItems();
        fireListReset();
    }

    /// <summary>
    ///     Inserts the specified item in the list at the specified index.
    /// </summary>
    /// <param name="index">The zero-based index where the item is to be inserted.</param>
    /// <param name="item">The item to insert in the list.</param>
    protected override void InsertItem(int index, T item)
    {
        EndNew(_addNewPos);
        base.InsertItem(index, item);
        if (_raiseItemChangedEvents)
            hookPropertyChanged(item);
        fireListChanged(ListChangedType.ItemAdded, index);
        CollectionChanged?.Invoke(this,
            new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, item,index));
    }

    /// <summary>
    ///     Removes the item at the specified index.
    /// </summary>
    /// <param name="index">The zero-based index of the item to remove. </param>
    /// <exception cref="T:System.NotSupportedException">
    ///     You are removing a newly added item and
    ///     <see cref="P:System.ComponentModel.IBindingList.AllowRemove" /> is set to false.
    /// </exception>
    protected override void RemoveItem(int index)
    {
        if (!_allowRemove && (_addNewPos < 0 || _addNewPos != index))
            throw new NotSupportedException();
        EndNew(_addNewPos);
        if (_raiseItemChangedEvents)
            unhookPropertyChanged(this[index]);
        var item = this[index];
        base.RemoveItem(index);
        fireListChanged(ListChangedType.ItemDeleted, index);
        CollectionChanged?.Invoke(this,
            new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, item,index));
    }

    /// <summary>
    ///     Replaces the item at the specified index with the specified item.
    /// </summary>
    /// <param name="index">The zero-based index of the item to replace.</param>
    /// <param name="item">The new value for the item at the specified index. The value can be null for reference types.</param>
    /// <exception cref="T:System.ArgumentOutOfRangeException">
    ///     <paramref name="index" /> is less than zero.-or-
    ///     <paramref name="index" /> is greater than <see cref="P:System.Collections.ObjectModel.Collection`1.Count" />.
    /// </exception>
    protected override void SetItem(int index, T item)
    {
        if (_raiseItemChangedEvents)
            unhookPropertyChanged(this[index]);
        base.SetItem(index, item);
        if (_raiseItemChangedEvents)
            hookPropertyChanged(item);
        fireListChanged(ListChangedType.ItemChanged, index);
        CollectionChanged?.Invoke(this,
            new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Replace, item,index));
    }

    /// <summary>
    ///     Adds a new item to the collection.
    /// </summary>
    /// <returns>
    ///     The item added to the list.
    /// </returns>
    /// <exception cref="T:System.InvalidOperationException">
    ///     The <see cref="P:System.Windows.Forms.BindingSource.AllowNew" />
    ///     property is set to false. -or-A public default constructor could not be found for the current item type.
    /// </exception>
    public T AddNew()
    {
        return (T) ((IBindingList) this).AddNew();
    }

    /// <summary>
    ///     Adds a new item to the end of the collection.
    /// </summary>
    /// <returns>
    ///     The item that was added to the collection.
    /// </returns>
    /// <exception cref="T:System.InvalidCastException">
    ///     The new item is not the same type as the objects contained in the
    ///     <see cref="T:System.ComponentModel.BindingList`1" />.
    /// </exception>
    protected virtual object AddNewCore()
    {
        var obj = fireAddingNew() ?? getNewInstance();
        Add((T) obj);
        return obj;
    }

    private static object getNewInstance()
    {
        return SecurityUtils.SecureCreateInstance(typeof (T));
    }

    /// <summary>
    ///     Sorts the items if overridden in a derived class; otherwise, throws a <see cref="T:System.NotSupportedException" />
    ///     .
    /// </summary>
    /// <param name="prop">A <see cref="T:System.ComponentModel.PropertyDescriptor" /> that specifies the property to sort on.</param>
    /// <param name="direction">One of the <see cref="T:System.ComponentModel.ListSortDirection" />  values.</param>
    /// <exception cref="T:System.NotSupportedException">Method is not overridden in a derived class. </exception>
    protected virtual void ApplySortCore(PropertyDescriptor prop, ListSortDirection direction)
    {
        throw new NotSupportedException();
    }

    /// <summary>
    ///     Removes any sort applied with
    ///     <see
    ///         cref="M:System.ComponentModel.BindingList`1.ApplySortCore(System.ComponentModel.PropertyDescriptor,System.ComponentModel.ListSortDirection)" />
    ///     if sorting is implemented in a derived class; otherwise, raises <see cref="T:System.NotSupportedException" />.
    /// </summary>
    /// <exception cref="T:System.NotSupportedException">Method is not overridden in a derived class. </exception>
    protected virtual void RemoveSortCore()
    {
        throw new NotSupportedException();
    }

    /// <summary>
    ///     Searches for the index of the item that has the specified property descriptor with the specified value, if
    ///     searching is implemented in a derived class; otherwise, a <see cref="T:System.NotSupportedException" />.
    /// </summary>
    /// <returns>
    ///     The zero-based index of the item that matches the property descriptor and contains the specified value.
    /// </returns>
    /// <param name="prop">The <see cref="T:System.ComponentModel.PropertyDescriptor" /> to search for.</param>
    /// <param name="key">
    ///     The value of
    ///     <paramref>
    ///         <name>property</name>
    ///     </paramref>
    ///     to match.
    /// </param>
    /// <exception cref="T:System.NotSupportedException">
    ///     <see cref="M:System.ComponentModel.BindingList`1.FindCore(System.ComponentModel.PropertyDescriptor,System.Object)" />
    ///     is not overridden in a derived class.
    /// </exception>
    protected virtual int FindCore(PropertyDescriptor prop, object key)
    {
        throw new NotSupportedException();
    }

    private void hookPropertyChanged(T item)
    {
        var notifyPropertyChanged = (object) item as INotifyPropertyChanged;
        if (notifyPropertyChanged == null)
            return;
        if (_propertyChangedEventHandler == null)
            _propertyChangedEventHandler = Child_PropertyChanged;
        notifyPropertyChanged.PropertyChanged += _propertyChangedEventHandler;
    }

    private void unhookPropertyChanged(T item)
    {
        var notifyPropertyChanged = (object) item as INotifyPropertyChanged;
        if (notifyPropertyChanged == null || _propertyChangedEventHandler == null)
            return;
        notifyPropertyChanged.PropertyChanged -= _propertyChangedEventHandler;
    }

    private void Child_PropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        if (!RaiseListChangedEvents)
            return;
        if (sender != null && e != null)
        {
            if (!string.IsNullOrEmpty(e.PropertyName))
            {
                T obj;
                try
                {
                    obj = (T) sender;
                }
                catch (InvalidCastException)
                {
                    ResetBindings();
                    return;
                }
                var newIndex = _lastChangeIndex;
                if (newIndex < 0 || newIndex >= Count || !this[newIndex].Equals(obj))
                {
                    newIndex = IndexOf(obj);
                    _lastChangeIndex = newIndex;
                }
                if (newIndex == -1)
                {
                    unhookPropertyChanged(obj);
                    ResetBindings();
                    return;
                }
                if (_itemTypeProperties == null)
                    _itemTypeProperties = TypeDescriptor.GetProperties(typeof (T));
                var propDesc = _itemTypeProperties.Find(e.PropertyName, true);
                OnListChanged(new ListChangedEventArgs(ListChangedType.ItemChanged, newIndex, propDesc));
                return;
            }
        }
        ResetBindings();
    }
}