WPF：如何挂钩 ListView 的 ItemsSource CollectionChanged 通知？

Question

我有一个 ListView 数据绑定到 ObservableCollection ...

<ListView x:Name="List1" ItemsSource="{Binding MyList}" />

我似乎找不到集合更改时触发的任何事件，所以我想不知何故，我需要以某种方式连接到集合更改通知？我不太确定该怎么做。

基本上，当集合发生变化时，我想做的工作超出了 ListView 在更新其列表方面已经完成的工作。

Answer 1

默认情况下，ItemsSource 的类型为 <代码>IEnumerable。您需要首先转换为可以访问 CollectionChanged 事件，然后为该事件添加处理程序。

((INotifyCollectionChanged)List1.ItemsSource).CollectionChanged +=
    new NotifyCollectionChangedEventHandler(List1CollectionChanged);

public void List1CollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)
{
    // Your logic here
}

---

Note: I cast it to INotifyCollectionChanged in my example, but you can really cast it to any object that implements that. Though, as a best practice, you should cast to the most generic type that gives you access to the methods/properties/events you need. So, while you can cast it to an ObservableCollection, you don't need to. INotifyCollectionChanged contains the event you need and if you ever decide to use some other type of collection that implements it, this will continue to work, whereas casting to an ObservableCollection means that if you one day decide that you're list is now of type MyOwnTypeOfObservableCollectionNotDerivedFromObservableCollection than this will break. ;)

PS 这应该放在 xaml 代码隐藏中。

Answer 2

您必须将处理程序附加到您的列表中。或者，使用 < code>CollectionView 并在那里挂钩更改的事件。

在你的代码隐藏中，这样做：

MyList.CollectionChanged += new NotifyCollectionChangedEventHandler( this.MyCollectionChanged );


private void SortCollectionChanged( object sender, NotifyCollectionChangedEventArgs e )
{
  Debug.WriteLine( "Changed" );
}

Answer 3

ObservableCollection{T} 公开 INotifyCollectionChanged.CollectionChanged< /a> 事件。当绑定到 ItemsSource 时，数据绑定引擎会处理从源到项目控件的更改，但如果您需要执行其他处理，您可以将处理程序附加到 CollectionChanged 事件并使用 NotifyCollectionChangedEventArgs 它提供了。

假设您的视图模型上有一个名为 MyList 的公共属性：

public ObservableCollection<T> MyList
{
  get
  {
    if(_viewModelMyList == null)
    {
      _viewModelMyList = new ObservableCollection<T>;
      _viewModelMyList.CollectionChanged += (o, e) => 
      {
        // code to process change event can go here
        if(e.Action == NotifyCollectionChangedAction.Add)
        {
        }
      };
    }
    return _viewModelMyList;
  }
}
private ObservableCollection<T> _viewModelMyList;