获取对触发更改事件的 ObservableCollection 的引用

Question

ObservableCollection 公开 CollectionChanged 事件。从该事件的处理程序有没有办法获得对触发事件的 ObservableCollection 的引用？我原以为 sender 参数是 ObservableCollection，但事实并非如此。

此代码示例说明 10 个 ObservableCollections 都将其 CollectionChanged 事件注册到一个方法。从那一种方法中，我想获得对已更改的 ObservableCollection 的引用：

internal class Program
{
    private static void Main(string[] args)
    {
        List<ObservableCollection<int>> collections = new List<ObservableCollection<int>>();

        for (int i = 0; i < 10; i++)
        {
            ObservableCollection<int> collection = new ObservableCollection<int>();
            collection.CollectionChanged += CollectionOnCollectionChanged;
            collections.Add(collection);
        }

        collections[5].Add(1234);
    }

    private static void CollectionOnCollectionChanged(object sender, NotifyCollectionChangedEventArgs notifyCollectionChangedEventArgs)
    {
        if (notifyCollectionChangedEventArgs.Action == NotifyCollectionChangedAction.Add)
        {
            // Before proceeding I need to get a reference to the ObservableCollection<int> where the change occured which fired this event.
        }
    }
}

查看传递给事件处理程序的参数，我没有看到对 ObservableCollection 的引用，所以我假设我无法得到它。

Answer 1

sender 对象是触发事件的ObservableCollection 的实例。你可以投射它。

 private static void CollectionOnCollectionChanged(object sender, NotifyCollectionChangedEventArgs notifyCollectionChangedEventArgs)
 {
     if (notifyCollectionChangedEventArgs.Action == NotifyCollectionChangedAction.Add)
     {
         ObservableCollection<int> myCollection = sender as ObservableCollection<int>;
         if(myCollection != null){
             //do whatever you want
         }
     }
 }

Answer 2

您还有一个选择是使用内联委托并在集合上形成一个闭包，如下所示：

private static void Main(string[] args)
{
    List<ObservableCollection<int>> collections = new List<ObservableCollection<int>>();

    for (int i = 0; i < 10; i++)
    {
        ObservableCollection<int> collection = new ObservableCollection<int>();
        collection.CollectionChanged += (s, e) =>
        {
            if (e.Action == NotifyCollectionChangedAction.Add)
            {
                // Can reference `collection` directly here
            }
        };
        collections.Add(collection);
    }

    collections[5].Add(1234);
}

sender 对象的存档转换（我觉得很乱。）

另一种写法可能是：

private static void Main(string[] args)
{
    List<ObservableCollection<int>> collections =
        Enumerable
            .Range(0, 10)
            .Select(n => new ObservableCollection<int>())
            .ToList();

    collections
        .ForEach(collection =>
        {
            collection.CollectionChanged += (s, e) =>
            {
                if (e.Action == NotifyCollectionChangedAction.Add)
                {
                    // Can reference `collection` directly here
                }
            };
        });

    collections[5].Add(1234);
}