c# - 如何在 protected 中实现接口(interface)成员？

Question

当我在 VS 2008 中看到 ReadOnlyObservableCollection 的元数据时，我感到非常惊讶......

public class ReadOnlyObservableCollection<T> : ReadOnlyCollection<T>, INotifyCollectionChanged, INotifyPropertyChanged
{
    // Summary:
    //     Initializes a new instance of the System.Collections.ObjectModel.ReadOnlyObservableCollection<T>
    //     class that serves as a wrapper for the specified System.Collections.ObjectModel.ObservableCollection<T>.
    //
    // Parameters:
    //   list:
    //     The collection to wrap.
    public ReadOnlyObservableCollection(ObservableCollection<T> list);

    // Summary:
    //     Occurs when an item is added or removed.
    protected virtual event NotifyCollectionChangedEventHandler CollectionChanged;
    //
    // Summary:
    //     Occurs when a property value changes.
    protected virtual event PropertyChangedEventHandler PropertyChanged;

    // Summary:
    //     Raises the System.Collections.ObjectModel.ReadOnlyObservableCollection<T>.CollectionChanged
    //     event.
    //
    // Parameters:
    //   args:
    //     The event data.
    protected virtual void OnCollectionChanged(NotifyCollectionChangedEventArgs args);
    //
    // Summary:
    //     Raises the System.Collections.ObjectModel.ReadOnlyObservableCollection<T>.PropertyChanged
    //     event.
    //
    // Parameters:
    //   args:
    //     The event data.
    protected virtual void OnPropertyChanged(PropertyChangedEventArgs args);
}

如您所见，CollectionChanged(INotifyCollectionChanged 的​​成员)是在 protected 中实现的...而我无法在自己的类中执行此操作。

.NET 框架不应编译!

有人能解释一下这个谜团吗？

Answer 1

如果您仔细检查 ReadOnlyObservableCollection，您会发现它显式实现了 INotifyPropertyChanged。换句话说， protected 事件处理程序并不是接口(interface)的真正实现 - INotifyCollectionChanged.CollectionChanged是。