Question

我已经对stackoverflow做了一些研究和其他答案，表明我需要扩展ObservableCollection类，在添加或删除项目时为每个项目添加PropertyChanged事件处理程序，以便在项目的内容中获取事件。集合改变......真的有点讨厌，但我已经根据其中一些答案实现了这个类：

    public class DeeplyObservableCollection<T> : ObservableCollection<T>
where T : INotifyPropertyChanged
{
    public DeeplyObservableCollection()
        : base()
    {
        CollectionChanged += new NotifyCollectionChangedEventHandler(DeeplyObservableCollection_CollectionChanged);
    }

    void DeeplyObservableCollection_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        if (e.NewItems != null)
        {
            foreach (Object item in e.NewItems)
            {
                (item as INotifyPropertyChanged).PropertyChanged += new PropertyChangedEventHandler(item_PropertyChanged);
            }
        }
        if (e.OldItems != null)
        {
            foreach (Object item in e.OldItems)
            {
                (item as INotifyPropertyChanged).PropertyChanged -= new PropertyChangedEventHandler(item_PropertyChanged);
            }
        }

    }

    void item_PropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        NotifyCollectionChangedEventArgs a = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset);
        OnCollectionChanged(a);
    }
}

据我了解，当其中一个元素触发PropertyChanged事件时，将触发CollectionChanged事件。当我逐步执行代码时，这似乎有效，因为我从item_PropertyChanged方法进入了DeeplyObservableCollection_CollectionChanged方法。

所以在我的代码中，我将一个事件处理程序附加到DeeplyObservableCollection_CollectionChanged方法，如下所示：

GroupSettingsList.CollectionChanged += new NotifyCollectionChangedEventHandler(this.ContentCollectionChanged);

GroupSettingsList是DeeplyObservableCollection，ContentCollectionChanged是CollectionChanged事件处理程序。我没有得到任何错误，但我的方法永远不会被调用，我不知道为什么。

我需要做什么才能在此处调用我的事件处理程序？

附加代码显示我如何使用此类：

    class MyViewModel : ViewModelBase
{

    private DeeplyObservableCollection<GroupSettings> _groupSettingsList;

    public MyViewModel()
    {
    GroupSettingsList = new DeeplyObservableCollection<GroupSettings>();

    GroupSettingsList.CollectionChanged += new NotifyCollectionChangedEventHandler(this.ContentCollectionChanged);

    // Have also tried this:
    // _groupSettingsList.CollectionChanged += new NotifyCollectionChangedEventHandler(this.ContentCollectionChanged);
}

public class GroupSettings : INotifyPropertyChanged
{
    private bool _isDisplayed;

    public bool IsDisplayed
    {
        get { return _isDisplayed; }
        set
        {
            _isDisplayed = value;
            this.OnPropertyChanged("IsDisplayed");
        }
    }

    public event System.ComponentModel.PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(String propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new System.ComponentModel.PropertyChangedEventArgs(propertyName));
        }
    }
}

public DeeplyObservableCollection<GroupSettings> GroupSettingsList
{
    get { return _groupSettingsList; }
    set
    {
        _groupSettingsList = value;


          this.OnPropertyChanged("GroupSettingsList");
        }
    }

    private void ContentCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        DoSomething(); // This never executes.
    }
}

为什么不调用我的CollectionChanged事件处理程序？

附加代码显示我如何使用此类：

0 个答案: