1

我有这个DependencyProperty包含一个属性为集合（ShoutBox.Entities）的实体：

public static readonly DependencyProperty ShoutBoxProperty = DependencyProperty.Register("ShoutBox",typeof (ShoutBox),typeof (ShoutBoxViewerControl));

public ShoutBox ShoutBox
{
    get { return (ShoutBox) GetValue(ShoutBoxProperty); }
    set { SetValue(ShoutBoxProperty, value); }
}

xaml它像这样被绑定：

<ItemsControl ItemsSource="{Binding ShoutBox.Entries}">
.
.
</ItemsControl>

当我第一次绑定它时，它按预期工作，但有时我需要将项目添加到集合中（使用同一控件中的方法），如下所示：

public void AddNewEntry(ShoutBoxEntry newEntry)
{
    Dispatcher.Invoke(new Action(() =>{
        ShoutBox.Entries.Add(newEntry); //Adding directly the the Dependency property
    }));
}

问题是当我使用上述方法添加一个新元素时，该项目没有显示在ItemsControl.

我的问题是，为什么我添加的新元素没有显示在ItemsControl?

[编辑]

Entries( ShoutBox.Entries ) 是类型List<ShoutBoxEntry>

4

2 回答 2

3

参赛作品的类型是什么？它要么需要 ObservableCollection，要么实现 ICollectionChanged。否则绑定不知道已添加新项目。

于 2009-05-10T16:50:44.257 回答
0

更改条目的类型确实应该可以解决问题...如果您想避免显式调用 Dispatcher.Invoke，我编写了一个集合，该集合在创建集合的线程上引发 CollectionChanged 和 PropertyChanged 事件：

public class AsyncObservableCollection<T> : ObservableCollection<T>
{
    private SynchronizationContext _synchronizationContext = SynchronizationContext.Current;

    public AsyncObservableCollection()
    {
    }

    public AsyncObservableCollection(IEnumerable<T> list)
        : base(list)
    {
    }

    protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
    {
        if (SynchronizationContext.Current == _synchronizationContext)
        {
            // Execute the CollectionChanged event on the current thread
            RaiseCollectionChanged(e);
        }
        else
        {
            // Post the CollectionChanged event on the creator thread
            _synchronizationContext.Post(RaiseCollectionChanged, e);
        }
    }

    private void RaiseCollectionChanged(object param)
    {
        // We are in the creator thread, call the base implementation directly
        base.OnCollectionChanged((NotifyCollectionChangedEventArgs)param);
    }

    protected override void OnPropertyChanged(PropertyChangedEventArgs e)
    {
        if (SynchronizationContext.Current == _synchronizationContext)
        {
            // Execute the PropertyChanged event on the current thread
            RaisePropertyChanged(e);
        }
        else
        {
            // Post the PropertyChanged event on the creator thread
            _synchronizationContext.Post(RaisePropertyChanged, e);
        }
    }

    private void RaisePropertyChanged(object param)
    {
        // We are in the creator thread, call the base implementation directly
        base.OnPropertyChanged((PropertyChangedEventArgs)param);
    }
}

更多细节可以在这里找到： http ://www.thomaslevesque.com/2009/04/17/wpf-binding-to-an-asynchronous-collection/

于 2009-05-10T22:58:52.810 回答