c# - 合并的 ObservableCollection

Question

我有两个 ObservableCollections，我需要在一个 ListView 控件中同时显示它们。为此，我创建了 MergedCollection，它将这两个集合呈现为一个 ObservableCollection。这样我就可以将 ListView.ItemsSource 设置为我的合并集合，并且列出两个集合。添加工作正常，但是当我尝试删除项目时，显示未处理的异常:

An unhandled exception of type 'System.InvalidOperationException' occurred in PresentationFramework.dll
Additional information: Added item does not appear at given index '2'.

MergedCollection 的代码如下:

public class MergedCollection : IEnumerable, INotifyCollectionChanged
{
    ObservableCollection<NetworkNode> nodes;
    ObservableCollection<NodeConnection> connections;

    public MergedCollection(ObservableCollection<NetworkNode> nodes, ObservableCollection<NodeConnection> connections)
    {
        this.nodes = nodes;
        this.connections = connections;

        this.nodes.CollectionChanged += new NotifyCollectionChangedEventHandler(NetworkNodes_CollectionChanged);
        this.connections.CollectionChanged += new NotifyCollectionChangedEventHandler(Connections_CollectionChanged);
    }

    void NetworkNodes_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        CollectionChanged(this, e);
    }

    void Connections_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        CollectionChanged(this, e);
    }

    #region IEnumerable Members

    public IEnumerator GetEnumerator()
    {
        for (int i = 0; i < connections.Count; i++)
        {
            yield return connections[i];
        }

        for (int i = 0; i < nodes.Count; i++)
        {
            yield return nodes[i];
        }
    }

    #endregion

    #region INotifyCollectionChanged Members

    public event NotifyCollectionChangedEventHandler CollectionChanged;

    #endregion
}

问候

Answer 1

有什么理由不能使用 CompositeCollection ？

抛出异常的原因是您没有将内部集合的索引转换为外部集合。您只是将完全相同的事件参数传递给外部事件(在 MergedCollection 上)，这就是为什么 WPF 找不到索引告诉它找到它们的项目。

您可以像这样使用 CompositeCollection:

<ListBox>
  <ListBox.Resources>
    <CollectionViewSource x:Key="DogCollection" Source="{Binding Dogs}"/>
    <CollectionViewSource x:Key="CatCollection" Source="{Binding Cats}"/>
  </ListBox.Resources>
  <ListBox.ItemsSource>
    <CompositeCollection>
      <CollectionContainer Collection="{Binding Source={StaticResource DogCollection}}"/>
      <CollectionContainer Collection="{Binding Source={StaticResource CatCollection}}"/>
    </CompositeCollection>
   </ListBox.ItemsSource>
   <!-- ... -->
</ListBox>

有关详细信息，请参阅 this answer .