c#-4.0 - 该事件只能出现在 = 或 -= 的左侧

Question

我在这段代码中有一些问题..任何人都可以帮助我

public event EventHandler CollectionChanged
        {
            [MethodImpl(MethodImplOptions.Synchronized)]
            add
            {
                this.CollectionChanged = (EventHandler)Delegate.Combine(this.CollectionChanged, value);
            }
            [MethodImpl(MethodImplOptions.Synchronized)]
            remove
            {
                this.CollectionChanged = (EventHandler)Delegate.Remove(this.CollectionChanged, value);
            }
        }

问候萨瓦