From:?http://www.xuebuyuan.com/841530.html

在講如何獲取多個返回值之前先來看一個小例子：

?

??????? private void button1_Click(object sender, EventArgs e)
??????? {
??????????? int Number = 200;???????? //設置Number的值為 200。
??????????? Publishser pub = new Publishser();?????//實例化Publishser
??????????? Subscriber1 sub1 = new Subscriber1();?????//實例化Subscriber1
??????????? Subscriber2 sub2 = new Subscriber2();?????//實例化Subscriber2
??????????? Subscriber3 sub3=new Subscriber3();???????//實例化Subscriber3
??????????? pub.NumberChanged += sub1.OnNumberChanged;???//將方法綁定到委托
??????????? pub.NumberChanged += sub2.OnNumberChanged;
??????????? pub.NumberChanged += sub3.OnNumberChanged;
??????????? pub.DoComething(Number);??????//調用DoComething
??????? }

??? class Publishser
??? {
??????? public delegate int DemoEventHandler(int num);??????//定義委托，可代表的方法類型是整形
??????? 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("調用了Subscriber1類，num值為："+ num);
??????????? return num + 100; ;
??????? }
??? }

??? class Subscriber2
??? {
??????? public int OnNumberChanged(int num)
??????? {
??????????? MessageBox.Show("調用了Subscriber2類 num值為："+num);
??????????? return num+100;
??????? }
??? }

??? class Subscriber3
??? {
??????? public int OnNumberChanged(int num)
??????? {
??????????? MessageBox.Show("調用了Subcriber3類，num值為："+num);
??????????? return num+100;
??????? }
??? }

?

?

?

?我以為得到的結果是：

????????????????????????????? 調用了Subscriber1類，num值為：200

????????????????????????????? 調用了Subscriber2類，num值為：300

????????????????????????????? 調用了Subscriber3類，num值為：400

????????????????????????????? 500

但是程序運行完之后結果卻不是我所想的，結果是：

??????????????????????????????????????????????????????????????????? 調用了Subscriber1類，num值為：200

??????????????????????????????????????????????????????????????????? 調用了Subscriber2類，num值為：200

??????????????????????????????????????????????????????????????????? 調用了Subscriber3類，num值為：200

????????????????????????????????????????????????????????????????????300

發現問題之后我用逐語句運行的方式調試程序，我發現當NumberChanged != null 第一次調用了Subscriber1之后并沒有返回到Publishser類，也沒有執行Subscriber1的 return，而是直接調用了Subscriber2，temp的值依舊是剛開始的200。執行完之后調用Subscriber3，只有當Subscriber3執行完了之后才返回到Publishser 這個時候temp的值等于300。（現在我也不知道為什么會這樣，但是我在網上學習了一種可以獲取多個返回值的方法！）

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

獲取多個返回值：

?

??????? 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("調用了Subscriber1類，num值為："+ num);
??????????? return num + 100; ;
??????? }
??? }

??? class Subscriber2
??? {
??????? public int OnNumberChanged(int num)
??????? {
??????????? MessageBox.Show("調用了Subscriber2類 num值為："+num);
??????????? return num+100;
??????? }
??? }

??? class Subscriber3
??? {
??????? public int OnNumberChanged(int num)
??????? {
??????????? MessageBox.Show("調用了Subcriber3類，num值為："+num);
??????????? return num+100;
??????? }
??? }

運行得到的結果是：

????????????????????????????? 調用了Subscriber1類，num值為：200

????????????????????????????? 調用了Subscriber2類，num值為：300

????????????????????????????? 調用了Subscriber3類，num值為：400

????????????????????????????? 500

?

現在就是我想到的結果了，利用Delegate 基類的GetInvocationList()靜態方法，可以得到委托鏈表，隨后遍歷委托鏈表依次執行，就可以得到每個方法的返回值了。

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