CollectionChanged - 集合名称

Question

我已经像这里一样为 ObservableCollection 实现了 CollectionChanged： Implementing CollectionChanged

是否有可能在 OnCollectionChanged 方法中找出更改的属性的名称是什么？

编辑： 如果 class 有任何变化，则应写入历史记录。我想实现三种情况：

"Normal" 属性改变了(string, int, ...): this is already 工作
在集合中添加和删除：如果我知道已更改集合的名称就可以工作

属性已更改：与 2) 相同的问题我不知道 ch

的名称（和索引）

public class ParentClass : BaseModel
{
    public ParentClass()
    {
        Children = new ObservableCollection<SomeModel>();
        Children.CollectionChanged += Oberservable_CollectionChanged;
    }

    private string id;

    public string Id
    {
        get
        {
            return id;
        }
        set
        {
            string oldId = id;
            id = value;
            OnPropertyChanged(oldArticleId,id);
        }
    }

    public ObservableCollection<SomeModel> Children { get; set; }

    protected virtual void OnPropertyChanged(object oldValue, object newValue, [CallerMemberName] string propertyName = null)
    {
        //1) Entry is added to history (this part is working)
    }


    protected void Oberservable_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
    {
        if (e.NewItems != null)
        {
            foreach (INotifyPropertyChanged added in e.NewItems)
            {
                added.PropertyChanged += OnPropertyChangedHandler;
                OnCollectionChanged(CollectionChangedModel.Action.Added, added);
            }
        }

        if (e.OldItems != null)
        {
            foreach (INotifyPropertyChanged removed in e.OldItems)
            {
                removed.PropertyChanged -= OnPropertyChangedHandler;
                OnCollectionChanged(CollectionChangedModel.Action.Removed, removed);
            }
        }
    }

    protected virtual void OnCollectionChanged(CollectionChangedModel.Action action, object value)
    {
        //2) TODO: History should be written, but I don't have the property name
    }

    public void OnPropertyChangedHandler(object sender, PropertyChangedEventArgs propertyChangedEventArgs)
    {
        //3) TODO: History about changed property in child-class (not working because of missing property name and index)
    }
}

Answer 1

这是正确的：

Children = new ObservableCollection<SomeModel>();
Children.CollectionChanged += Oberservable_CollectionChanged;

尽管您必须确保没有人会更改集合，例如像这样：

public ObservableCollection<SomeModel> Children { get; }

或者在 setter.

中使其成为完整的属性和 subscribing/unsubscribing

现在关于 Oberservable_CollectionChanged 处理程序：

Add and remove in collections: would be working if I know the name of the changed collection

将 sender 添加到您的活动中。将参数包装到 ...EventArgs class 中（使其不可变），参见 msdn.

public event EventHandler<MyCollectionChangedEventArgs> CollectionChanged;
protected virtual void OnCollectionChanged(object sender, MyCollectionChangedEventArgs e)
{
    //2) TODO: History should be written, but I don't have the property name

    // sender is name
    // e.Action and e.Value are parameters
}

Property inside a collection is changed: same problem as 2) I don't know the name (and index) of the ch

将事件处理程序包装到包含事件处理程序和您需要的值的实例中（我将把该任务留给您）。如果不需要取消订阅，这可以通过使用 lamdba 闭包轻松实现：

foreach (var added in e.NewItems.OfType<INotifyPropertyChanged>)
{
    added.PropertyChanged += (s, e) => 
    {
        // you have `sender` here in addition to `s`, clever?
    };
}

CollectionChanged - 集合名称

CollectionChanged - Name of Collection

c#

inotifycollectionchanged