c# - 将多个 ObservableCollection 绑定到一个 ObservableCollection

Question

有一堆ObservableCollection<MeClass> Result并需要将它们全部组合成另一个ObservableCollection<MeClass> AllResults，以便我可以将其显示在listview.

只是不知道如何将它们组合在一起。

我创建了一个新类来组合它们，但不确定在获得列表后它们将如何更新......所以不太确定要采取哪个方向。

我知道INotifyPropertyChanged我只是不确定如何将它们结合起来并随着一切的变化而不断更新。

Answer 1

.NETCompositeCollection允许您将多个集合视为一个集合。它实现INotifyCollectionChanged了 ，因此只要您的内部集合也实现INotifyCollectionChanged了（在您的情况下确实如此），您的绑定应该可以正常工作。

使用示例：

CompositeCollection cc = new CompositeCollection();
CollectionContainer container1 = new CollectionContainer() { Collection = Result1 }
CollectionContainer container2 = new CollectionContainer() { Collection = Result2 }
cc.Add(container1);
cc.Add(container2);

Answer 2

像这样的东西？

public class CompositeCollection : ObservableCollection<MeClass>
{
    private ObservableCollection<MeClass> _subCollection1;
    private ObservableCollection<MeClass> _subCollection2;

    public CompositeCollection(ObservableCollection<MeClass> subCollection1, ObservableCollection<MeClass> subCollection2) 
    {
        _subCollection1 = subCollection1;
        _subCollection2 = subCollection2;

        AddSubCollections();
        SubscribeToSubCollectionChanges();
    }

    private void AddSubCollections()
    {
        AddItems(_subCollection1.All);
        AddItems(_subCollection2.All);
    }

    private void AddItems(IEnumerable<MeClass> items)
    {
        foreach (MeClass me in items)
            Add(me);
    }

    private void RemoveItems(IEnumerable<MeClass> items)
    {
        foreach (MeClass me in items)
            Remove(me);
    }

    private void SubscribeToSubCollectionChanges()
    {
        _subCollection1.CollectionChanged += OnSubCollectionChanged;
        _subCollection2.CollectionChanged += OnSubCollectionChanged;
    }

    private void OnSubCollectionChanged(object source, NotifyCollectionChangedEventArgs args)
    {
        switch(args.Action)
        {
            case NotifyCollectionChangedAction.Add:    AddItems(args.NewItems.Cast<MeClass>());
                                                       break;

            case NotifyCollectionChangedAction.Remove: RemoveItems(args.OldItems.Cast<MeClass>());
                                                       break;

            case NotifyCollectionChangedAction.Reset:  Clear();
                                                       AddSubCollections();
                                                       break;
        }
    }
}

Answer 3

我将@GazTheDestroyer 的答案改写成这个（需要 C# 7）：

internal sealed class CompositeObservableCollection<T> : ObservableCollection<T>
{
    public CompositeObservableCollection(INotifyCollectionChanged subCollection1, INotifyCollectionChanged subCollection2)
    {
        AddItems((IEnumerable<T>)subCollection1);
        AddItems((IEnumerable<T>)subCollection2);

        subCollection1.CollectionChanged += OnSubCollectionChanged;
        subCollection2.CollectionChanged += OnSubCollectionChanged;

        void OnSubCollectionChanged(object source, NotifyCollectionChangedEventArgs args)
        {
            switch (args.Action)
            {
                case NotifyCollectionChangedAction.Add:
                    AddItems(args.NewItems.Cast<T>());
                    break;
                case NotifyCollectionChangedAction.Remove:
                    RemoveItems(args.OldItems.Cast<T>());
                    break;
                case NotifyCollectionChangedAction.Reset:
                    Clear();
                    AddItems((IEnumerable<T>)subCollection1);
                    AddItems((IEnumerable<T>)subCollection2);
                    break;
                case NotifyCollectionChangedAction.Replace:
                    RemoveItems(args.OldItems.Cast<T>());
                    AddItems(args.NewItems.Cast<T>());
                    break;
                case NotifyCollectionChangedAction.Move:
                    throw new NotImplementedException();
                default:
                    throw new ArgumentOutOfRangeException();
            }
        }

        void AddItems(IEnumerable<T> items)
        {
            foreach (var me in items)
                Add(me);
        }

        void RemoveItems(IEnumerable<T> items)
        {
            foreach (var me in items)
                Remove(me);
        }
    }
}