调用委托按引用相等进行比较：.Equals()
Action action1 = () => Console.WriteLine("Hello delegates");
Action action2 = () => Console.WriteLine("Hello delegates");
Action action1Again = action1;
Console.WriteLine(action1.Equals(action1)) // 真正
Console.WriteLine(action1.Equals(action2)) // 假
Console.WriteLine(action1Again.Equals(action1)) // 真正这些规则在进行多播委托时+=或-=在多播委托上也适用，例如，订阅和取消订阅事件时。