.Net （C#）委托和事件（获取多个返回值）

在讲如何获取多个返回值之前先来看一个小例子：

 

        private void button1_Click(object sender, EventArgs e)        {            int Number = 200;         //设置Number的值为 200。            Publishser pub = new Publishser();     //实例化Publishser            Subscriber1 sub1 = new Subscriber1();     //实例化Subscriber1            Subscriber2 sub2 = new Subscriber2();     //实例化Subscriber2            Subscriber3 sub3=new Subscriber3();       //实例化Subscriber3            pub.NumberChanged += sub1.OnNumberChanged;   //将方法绑定到委托            pub.NumberChanged += sub2.OnNumberChanged;            pub.NumberChanged += sub3.OnNumberChanged;            pub.DoComething(Number);      //调用DoComething        }

    class Publishser    {        public delegate int DemoEventHandler(int num);      //定义委托，可代表的方法类型是整形        public event DemoEventHandler NumberChanged;  //申明事件        public void DoComething(int temp)        {            if (NumberChanged != null)            {                 temp=NumberChanged(temp);            }            MessageBox.Show(temp.ToString());        }    }

    class Subscriber1    {        public int OnNumberChanged(int num)        {            MessageBox.Show("调用了Subscriber1类，num值为："+ num);            return num + 100; ;        }    }

    class Subscriber2    {        public int OnNumberChanged(int num)        {            MessageBox.Show("调用了Subscriber2类 num值为："+num);            return num+100;        }    }

    class Subscriber3    {        public int OnNumberChanged(int num)        {            MessageBox.Show("调用了Subcriber3类，num值为："+num);            return num+100;        }    }

 

 

 

 我以为得到的结果是：

                              调用了Subscriber1类，num值为：200

                              调用了Subscriber2类，num值为：300

                              调用了Subscriber3类，num值为：400

                              500

但是程序运行完之后结果却不是我所想的，结果是：

                                                                    调用了Subscriber1类，num值为：200

                                                                    调用了Subscriber2类，num值为：200

                                                                    调用了Subscriber3类，num值为：200

                                                                    300

发现问题之后我用逐语句运行的方式调试程序，我发现当NumberChanged != null 第一次调用了Subscriber1之后并没有返回到Publishser类，也没有执行Subscriber1的 return，而是直接调用了Subscriber2，temp的值依旧是刚开始的200。执行完之后调用Subscriber3，只有当Subscriber3执行完了之后才返回到Publishser 这个时候temp的值等于300。（现在我也不知道为什么会这样，但是我在网上学习了一种可以获取多个返回值的方法！）

---------------------------------------------------------------------------------------------------------------------------------------

获取多个返回值：

 

        private void button1_Click(object sender, EventArgs e)        {            int Number = 200;            Publishser pub = new Publishser();            Subscriber1 sub1 = new Subscriber1();            Subscriber2 sub2 = new Subscriber2();            Subscriber3 sub3=new Subscriber3();            pub.NumberChanged += sub1.OnNumberChanged;            pub.NumberChanged += sub2.OnNumberChanged;            pub.NumberChanged += sub3.OnNumberChanged;            pub.DoComething(Number);        }

    class Publishser    {        public delegate int DemoEventHandler(int num);        public event DemoEventHandler NumberChanged;        public void DoComething(int temp)        {            if (NumberChanged != null)            {                Delegate[] delArray = NumberChanged.GetInvocationList();                  foreach (Delegate del in delArray)                {                    DemoEventHandler method = (DemoEventHandler)del;                    temp = method(temp);                }            }            MessageBox.Show(temp.ToString());        }    }

    class Subscriber1    {        public int OnNumberChanged(int num)        {            MessageBox.Show("调用了Subscriber1类，num值为："+ num);            return num + 100; ;        }    }

    class Subscriber2    {        public int OnNumberChanged(int num)        {            MessageBox.Show("调用了Subscriber2类 num值为："+num);            return num+100;        }    }

    class Subscriber3    {        public int OnNumberChanged(int num)        {            MessageBox.Show("调用了Subcriber3类，num值为："+num);            return num+100;        }    }

运行得到的结果是：

                              调用了Subscriber1类，num值为：200

                              调用了Subscriber2类，num值为：300

                              调用了Subscriber3类，num值为：400

                              500

 

现在就是我想到的结果了，利用Delegate 基类的GetInvocationList()静态方法，可以得到委托链表，随后遍历委托链表依次执行，就可以得到每个方法的返回值了。