NotifyCollectionChangedEventArgs.cs

Go to the documentation of this file.

namespace System.Collections.Specialized;
 
public class NotifyCollectionChangedEventArgs : EventArgs
{
    private readonly NotifyCollectionChangedAction _action;
 
    private readonly IList _newItems;
 
    private readonly IList _oldItems;
 
    private readonly int _newStartingIndex = -1;
 
    private readonly int _oldStartingIndex = -1;
 
    public NotifyCollectionChangedAction Action => _action;
 
    public IList? NewItems => _newItems;
 
    public IList? OldItems => _oldItems;
 
    public int NewStartingIndex => _newStartingIndex;
 
    public int OldStartingIndex => _oldStartingIndex;
 
    public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action)
    {
        if (action != NotifyCollectionChangedAction.Reset)
        {
            throw new ArgumentException(System.SR.Format(System.SR.WrongActionForCtor, NotifyCollectionChangedAction.Reset), "action");
        }
        _action = action;
    }
 
    public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, object? changedItem)
        : this(action, changedItem, -1)
    {
    }
 
    public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, object? changedItem, int index)
    {
        switch (action)
        {
        case NotifyCollectionChangedAction.Reset:
            if (changedItem != null)
            {
                throw new ArgumentException(System.SR.ResetActionRequiresNullItem, "action");
            }
            if (index != -1)
            {
                throw new ArgumentException(System.SR.ResetActionRequiresIndexMinus1, "action");
            }
            break;
        case NotifyCollectionChangedAction.Add:
            _newItems = new SingleItemReadOnlyList(changedItem);
            _newStartingIndex = index;
            break;
        case NotifyCollectionChangedAction.Remove:
            _oldItems = new SingleItemReadOnlyList(changedItem);
            _oldStartingIndex = index;
            break;
        default:
            throw new ArgumentException(System.SR.MustBeResetAddOrRemoveActionForCtor, "action");
        }
        _action = action;
    }
 
    public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, IList? changedItems)
        : this(action, changedItems, -1)
    {
    }
 
    public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, IList? changedItems, int startingIndex)
    {
        switch (action)
        {
        case NotifyCollectionChangedAction.Reset:
            if (changedItems != null)
            {
                throw new ArgumentException(System.SR.ResetActionRequiresNullItem, "action");
            }
            if (startingIndex != -1)
            {
                throw new ArgumentException(System.SR.ResetActionRequiresIndexMinus1, "action");
            }
            break;
        case NotifyCollectionChangedAction.Add:
        case NotifyCollectionChangedAction.Remove:
            if (changedItems == null)
            {
                throw new ArgumentNullException("changedItems");
            }
            if (startingIndex < -1)
            {
                throw new ArgumentException(System.SR.IndexCannotBeNegative, "startingIndex");
            }
            if (action == NotifyCollectionChangedAction.Add)
            {
                _newItems = new ReadOnlyList(changedItems);
                _newStartingIndex = startingIndex;
            }
            else
            {
                _oldItems = new ReadOnlyList(changedItems);
                _oldStartingIndex = startingIndex;
            }
            break;
        default:
            throw new ArgumentException(System.SR.MustBeResetAddOrRemoveActionForCtor, "action");
        }
        _action = action;
    }
 
    public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, object? newItem, object? oldItem)
        : this(action, newItem, oldItem, -1)
    {
    }
 
    public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, object? newItem, object? oldItem, int index)
    {
        if (action != NotifyCollectionChangedAction.Replace)
        {
            throw new ArgumentException(System.SR.Format(System.SR.WrongActionForCtor, NotifyCollectionChangedAction.Replace), "action");
        }
        _action = action;
        _newItems = new SingleItemReadOnlyList(newItem);
        _oldItems = new SingleItemReadOnlyList(oldItem);
        _newStartingIndex = (_oldStartingIndex = index);
    }
 
    public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, IList newItems, IList oldItems)
        : this(action, newItems, oldItems, -1)
    {
    }
 
    public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, IList newItems, IList oldItems, int startingIndex)
    {
        if (action != NotifyCollectionChangedAction.Replace)
        {
            throw new ArgumentException(System.SR.Format(System.SR.WrongActionForCtor, NotifyCollectionChangedAction.Replace), "action");
        }
        if (newItems == null)
        {
            throw new ArgumentNullException("newItems");
        }
        if (oldItems == null)
        {
            throw new ArgumentNullException("oldItems");
        }
        _action = action;
        _newItems = new ReadOnlyList(newItems);
        _oldItems = new ReadOnlyList(oldItems);
        _newStartingIndex = (_oldStartingIndex = startingIndex);
    }
 
    public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, object? changedItem, int index, int oldIndex)
    {
        if (action != NotifyCollectionChangedAction.Move)
        {
            throw new ArgumentException(System.SR.Format(System.SR.WrongActionForCtor, NotifyCollectionChangedAction.Move), "action");
        }
        if (index < 0)
        {
            throw new ArgumentException(System.SR.IndexCannotBeNegative, "index");
        }
        _action = action;
        _newItems = (_oldItems = new SingleItemReadOnlyList(changedItem));
        _newStartingIndex = index;
        _oldStartingIndex = oldIndex;
    }
 
    public NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction action, IList? changedItems, int index, int oldIndex)
    {
        if (action != NotifyCollectionChangedAction.Move)
        {
            throw new ArgumentException(System.SR.Format(System.SR.WrongActionForCtor, NotifyCollectionChangedAction.Move), "action");
        }
        if (index < 0)
        {
            throw new ArgumentException(System.SR.IndexCannotBeNegative, "index");
        }
        _action = action;
        _newItems = (_oldItems = ((changedItems != null) ? new ReadOnlyList(changedItems) : null));
        _newStartingIndex = index;
        _oldStartingIndex = oldIndex;
    }
}