ObservableCollection警告

上面提到的(Said Roohullah Allem)

ObservableCollection类的独特之处在于 类支持名为CollectionChanged的事件。

记住这一点……如果你在ObservableCollection中添加了大量的项目，UI也会更新很多次。这可能会阻塞或冻结你的UI。 一种解决方法是创建一个新列表，添加所有的项目，然后将属性设置为新列表。这只会触及UI一次。再次……这是为了添加大量的项目。

最大的用途之一是可以将UI组件绑定到一个组件上，如果集合的内容发生变化，它们将适当地响应。例如，如果你将一个ListView的ItemsSource绑定到一个，如果你修改了集合，ListView的内容将自动更新。

编辑: 下面是一些来自MSDN的示例代码: http://msdn.microsoft.com/en-us/library/ms748365.aspx

在c#中，将ListBox连接到集合非常简单

listBox.ItemsSource = NameListData;

但是如果你还没有将列表作为静态资源连接起来并定义NameItemTemplate，你可能想要重写PersonName的ToString()。例如:

public override ToString()
{
    return string.Format("{0} {1}", this.FirstName, this.LastName);
}

ObservableCollection警告

上面提到的(Said Roohullah Allem)

ObservableCollection类的独特之处在于 类支持名为CollectionChanged的事件。

记住这一点……如果你在ObservableCollection中添加了大量的项目，UI也会更新很多次。这可能会阻塞或冻结你的UI。 一种解决方法是创建一个新列表，添加所有的项目，然后将属性设置为新列表。这只会触及UI一次。再次……这是为了添加大量的项目。

从Pro c# 5.0和。net 4.5框架

The ObservableCollection<T> class is very useful in that it has the ability to inform external objects when its contents have changed in some way (as you might guess, working with ReadOnlyObservableCollection<T> is very similar, but read-only in nature). In many ways, working with the ObservableCollection<T> is identical to working with List<T>, given that both of these classes implement the same core interfaces. What makes the ObservableCollection<T> class unique is that this class supports an event named CollectionChanged. This event will fire whenever a new item is inserted, a current item is removed (or relocated), or if the entire collection is modified. Like any event, CollectionChanged is defined in terms of a delegate, which in this case is NotifyCollectionChangedEventHandler. This delegate can call any method that takes an object as the first parameter, and a NotifyCollectionChangedEventArgs as the second. Consider the following Main() method, which populates an observable collection containing Person objects and wires up the CollectionChanged event:

class Program
{
   static void Main(string[] args)
   {
     // Make a collection to observe and add a few Person objects.
     ObservableCollection<Person> people = new ObservableCollection<Person>()
     {
        new Person{ FirstName = "Peter", LastName = "Murphy", Age = 52 },
        new Person{ FirstName = "Kevin", LastName = "Key", Age = 48 },
     };
     // Wire up the CollectionChanged event.
     people.CollectionChanged += people_CollectionChanged;
     // Now add a new item.
     people.Add(new Person("Fred", "Smith", 32));

     // Remove an item.
     people.RemoveAt(0);

     Console.ReadLine();
   }
   static void people_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
   {
       // What was the action that caused the event?
        Console.WriteLine("Action for this event: {0}", e.Action);

        // They removed something. 
        if (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Remove)
        {
            Console.WriteLine("Here are the OLD items:");
            foreach (Person p in e.OldItems)
            {
                Console.WriteLine(p.ToString());
            }
            Console.WriteLine();
        }

        // They added something. 
        if (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Add)
        {
            // Now show the NEW items that were inserted.
            Console.WriteLine("Here are the NEW items:");
            foreach (Person p in e.NewItems)
            {
                Console.WriteLine(p.ToString());
            }
        }
   }
}

The incoming NotifyCollectionChangedEventArgs parameter defines two important properties, OldItems and NewItems, which will give you a list of items that were currently in the collection before the event fired, and the new items that were involved in the change. However, you will want to examine these lists only under the correct circumstances. Recall that the CollectionChanged event can fire when items are added, removed, relocated, or reset. To discover which of these actions triggered the event, you can use the Action property of NotifyCollectionChangedEventArgs. The Action property can be tested against any of the following members of the NotifyCollectionChangedAction enumeration:

public enum NotifyCollectionChangedAction
{
Add = 0,
Remove = 1,
Replace = 2,
Move = 3,
Reset = 4,
}

它是一个集合，用于通知大多数UI在集合中发生变化，它支持自动通知。

主要用于WPF，

假设你有一个带有列表框和add按钮的UI，当你点击按钮时，一个类型为suppose person的对象会被添加到observable集合中，你将这个集合绑定到Listbox的ItemSource，所以只要你在集合中添加了一个新项目，Listbox就会更新自己并在其中添加一个项目。

ObservableCollection本质上与常规集合类似，只是它实现了 的接口:

INotifyCollectionChanged, INotifyPropertyChanged

因此，当您想知道集合何时发生更改时，它非常有用。触发一个事件，告诉用户添加/删除或移动了哪些条目。

更重要的是，当在表单上使用数据绑定时，它们非常有用。