Question

我有这个清单：

List<string> x=new List<string>

所以，现在我想在计数增加时做点什么。我试过了：

if(x.Count++){
  //do stuff
}

但它没有用。那我该怎么办呢？

Answer 1

你不能像你想做的那样做。 if (x.Count++)毫无意义 - 您正试图递增计数（这是只读的）。

我会从List<T>派生并添加ItemAdded和ItemRemoved个事件。

实际上，这将重新发明轮子。这样的集合已经存在。请参阅ObservableCollection<T>，这会引发CollectionChanged事件。 NotifyCollectionChangedEventArgs会告诉您更改的内容。

示例（未测试）：

void ChangeHandler(object sender, NotifyCollectionChangedEventArgs e ) {
    switch (e.Action) {
        case NotifyCollectionChangedAction.Add:
            // One or more items were added to the collection.
            break;
        case NotifyCollectionChangedAction.Move:
            // One or more items were moved within the collection.
            break;
        case NotifyCollectionChangedAction.Remove:
            // One or more items were removed from the collection.
            break;
        case NotifyCollectionChangedAction.Replace:
            // One or more items were replaced in the collection.
            break;
        case NotifyCollectionChangedAction.Reset:
            // The content of the collection changed dramatically.
            break;
    }

    // The other properties of e tell you where in the list
    // the change took place, and what was affected.
}

void test() {
    var myList = ObservableCollection<int>();
    myList.CollectionChanged += ChangeHandler;

    myList.Add(4);
}

参考文献：

NotifyCollectionChangedAction

如何检查列表的数量是否增加？

1 个答案: