https://www.cnblogs.com/ecollab/p/6128679.html
系统自带的泛型委托
Action 无参数无返回值
Action<T> 没有返回值,最多有16个参数
Action<int> func = e => Console.WriteLine(e);
func(123)
Func 具有返回值,最多有16个参数
Func<int> f = () => 123;
Console.WriteLine(f() + 1);
List<string> list = new List<string>("赵晓虎,王小虎,乐虎,老虎,东北虎,华南虎".Split(','));
foreach (string item in list.Where(e => e.Contains("华"))) //Where,输入参数为字符串,返回参数为布尔
{
Console.WriteLine(item);
}
public class Person { public string Name { get; set; } public int Age { get; set; } public char Sex { get; set; }</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">override</span> <span style="color: rgba(0, 0, 255, 1)">string</span><span style="color: rgba(0, 0, 0, 1)"> ToString() { </span><span style="color: rgba(0, 0, 255, 1)">return</span> <span style="color: rgba(0, 0, 255, 1)">string</span>.Format(<span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">{0},{1}</span><span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(0, 0, 0, 1)">, Name, Age); } }
------------------------------------------------------------------
public delegate int MyCompareHandler(Person p1, Person p2);Sort(ps, (a, b) => string.Compare(a.Name, b.Name)); Sort(ps, (a, b) => a.Age - b.Age); } //冒泡排序</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)"> Program { </span><span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">void</span> Main(<span style="color: rgba(0, 0, 255, 1)">string</span><span style="color: rgba(0, 0, 0, 1)">[] args) { MyCompareHandler MyCompare </span>= <span style="color: rgba(0, 0, 255, 1)">null</span><span style="color: rgba(0, 0, 0, 1)">; Person[] ps </span>=<span style="color: rgba(0, 0, 0, 1)"> { </span><span style="color: rgba(0, 0, 255, 1)">new</span> Person() { Age=<span style="color: rgba(128, 0, 128, 1)">10</span>, Name=<span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">赵晓虎</span><span style="color: rgba(128, 0, 0, 1)">"</span>, Sex=<span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">男</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)"> }, </span><span style="color: rgba(0, 0, 255, 1)">new</span> Person() { Age=<span style="color: rgba(128, 0, 128, 1)">30</span>, Name=<span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">波波</span><span style="color: rgba(128, 0, 0, 1)">"</span>, Sex=<span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">男</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)"> }, </span><span style="color: rgba(0, 0, 255, 1)">new</span> Person() { Age=<span style="color: rgba(128, 0, 128, 1)">35</span>, Name=<span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">杨茜</span><span style="color: rgba(128, 0, 0, 1)">"</span>, Sex=<span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">女</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)"> }, </span><span style="color: rgba(0, 0, 255, 1)">new</span> Person() { Age=<span style="color: rgba(128, 0, 128, 1)">13</span>, Name=<span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">马伦</span><span style="color: rgba(128, 0, 0, 1)">"</span>, Sex=<span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(128, 0, 0, 1)">男</span><span style="color: rgba(128, 0, 0, 1)">'</span><span style="color: rgba(0, 0, 0, 1)"> } }; </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 排序 </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 比较 </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> int n = string.Compare("a", "b"); </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> MyCompare = CompareByAge; </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">MyCompare = CompareByName; </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">if (MyCompare != null) </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">{ </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> int num = MyCompare(ps[0], ps[1]); </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">} </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> MyCompareHandler compare = CompareByAge; </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> Sort(ps, compare); </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> Sort(ps, CompareByName);</span>
<span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> Sort(Person[] ps, MyCompareHandler compare) { </span><span style="color: rgba(0, 0, 255, 1)">if</span> (compare == <span style="color: rgba(0, 0, 255, 1)">null</span>) <span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)">; </span><span style="color: rgba(0, 0, 255, 1)">for</span> (<span style="color: rgba(0, 0, 255, 1)">int</span> i = <span style="color: rgba(128, 0, 128, 1)">0</span>; i < ps.Length - <span style="color: rgba(128, 0, 128, 1)">1</span>; i++<span style="color: rgba(0, 0, 0, 1)">) { </span><span style="color: rgba(0, 0, 255, 1)">for</span> (<span style="color: rgba(0, 0, 255, 1)">int</span> j = <span style="color: rgba(128, 0, 128, 1)">0</span>; j < ps.Length - i - <span style="color: rgba(128, 0, 128, 1)">1</span>; j++<span style="color: rgba(0, 0, 0, 1)">) { </span><span style="color: rgba(0, 0, 255, 1)">if</span> (compare(ps[j], ps[j + <span style="color: rgba(128, 0, 128, 1)">1</span>]) > <span style="color: rgba(128, 0, 128, 1)">0</span><span style="color: rgba(0, 0, 0, 1)">) { Person pTemp </span>=<span style="color: rgba(0, 0, 0, 1)"> ps[j]; ps[j] </span>= ps[j + <span style="color: rgba(128, 0, 128, 1)">1</span><span style="color: rgba(0, 0, 0, 1)">]; ps[j </span>+ <span style="color: rgba(128, 0, 128, 1)">1</span>] =<span style="color: rgba(0, 0, 0, 1)"> pTemp; } } } } </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">public static int CompareByAge(Person p1, Person p2) </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">{ </span><span style="color: rgba(0, 128, 0, 1)">//</span> <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> n1 > n2 => n1 - n2 > 0 </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> return p1.Age - p2.Age; </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">} </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">public static int CompareByName(Person p1, Person p2) </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">{ </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> return string.Compare(p1.Name, p2.Name); </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">}</span> }</pre>
委托计算器
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
public class Calculator { public static int AdditionMethod(int num1, int num2) { return num1 + num2; } public static int SubtractionMethod(int num1, int num2) { return num1 - num2; } public static int MultiplicationMethod(int num1, int num2) { return num1 * num2; } public static int DivisionMethod(int num1, int num2) { return num1 / num2; } }public delegate int MyCalculator(int n1, int n2);
class Program
{
static void Main(string[] args)
{
// 需要什么?
// 委托
// 实现加减乘除的方法
Console.WriteLine("请输入数字");
int num1 = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("请输入运算符");
string oper = Console.ReadLine();
Console.WriteLine("请输入数字");
int num2 = Convert.ToInt32(Console.ReadLine());MyCalculator cal </span>= <span style="color: rgba(0, 0, 255, 1)">null</span><span style="color: rgba(0, 0, 0, 1)">; </span><span style="color: rgba(0, 0, 255, 1)">switch</span><span style="color: rgba(0, 0, 0, 1)"> (oper) { </span><span style="color: rgba(0, 0, 255, 1)">case</span> <span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">+</span><span style="color: rgba(128, 0, 0, 1)">"</span>: cal = Calculator.AdditionMethod; <span style="color: rgba(0, 0, 255, 1)">break</span><span style="color: rgba(0, 0, 0, 1)">; </span><span style="color: rgba(0, 0, 255, 1)">case</span> <span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">-</span><span style="color: rgba(128, 0, 0, 1)">"</span>: cal = Calculator.SubtractionMethod; <span style="color: rgba(0, 0, 255, 1)">break</span><span style="color: rgba(0, 0, 0, 1)">; </span><span style="color: rgba(0, 0, 255, 1)">case</span> <span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">*</span><span style="color: rgba(128, 0, 0, 1)">"</span>: cal = Calculator.MultiplicationMethod; <span style="color: rgba(0, 0, 255, 1)">break</span><span style="color: rgba(0, 0, 0, 1)">; </span><span style="color: rgba(0, 0, 255, 1)">case</span> <span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">/</span><span style="color: rgba(128, 0, 0, 1)">"</span>: cal = Calculator.DivisionMethod; <span style="color: rgba(0, 0, 255, 1)">break</span><span style="color: rgba(0, 0, 0, 1)">; } </span><span style="color: rgba(0, 0, 255, 1)">if</span> (cal != <span style="color: rgba(0, 0, 255, 1)">null</span><span style="color: rgba(0, 0, 0, 1)">) { Console.WriteLine(</span><span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">{0}{1}{2}={3}</span><span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(0, 0, 0, 1)">, num1, oper, num2, cal(num1, num2)); } Console.ReadKey(); } }</span></pre>
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窗体传值
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
public partial class Form1 : Form { Random r = new Random(); public Form1() { InitializeComponent(); }}</span><span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">void</span> button1_Click(<span style="color: rgba(0, 0, 255, 1)">object</span><span style="color: rgba(0, 0, 0, 1)"> sender, EventArgs e) { ChangeColor(); } </span><span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> ChangeColor() { </span><span style="color: rgba(0, 0, 255, 1)">this</span>.BackColor = Color.FromArgb(r.Next(<span style="color: rgba(128, 0, 128, 1)">256</span>), r.Next(<span style="color: rgba(128, 0, 128, 1)">256</span>), r.Next(<span style="color: rgba(128, 0, 128, 1)">256</span><span style="color: rgba(0, 0, 0, 1)">)); } </span><span style="color: rgba(0, 0, 255, 1)">int</span> i = <span style="color: rgba(128, 0, 128, 1)">0</span><span style="color: rgba(0, 0, 0, 1)">; </span><span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">void</span> timer1_Tick(<span style="color: rgba(0, 0, 255, 1)">object</span><span style="color: rgba(0, 0, 0, 1)"> sender, EventArgs e) { </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">i += 10; </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> this.BackColor = Color.FromArgb(i, 256 - i, i);</span>
</span><span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">void</span> button2_Click(<span style="color: rgba(0, 0, 255, 1)">object</span><span style="color: rgba(0, 0, 0, 1)"> sender, EventArgs e) { </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 创建子窗体</span> Form2 f = <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> Form2(); </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 订阅方法</span> f.MyFunc +=<span style="color: rgba(0, 0, 0, 1)"> ChangeColor; f.Show(); } }
//////////////////////////////////////////////////////////////////////////
public partial class Form2 : Form
{
public event Action MyFunc;</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Form2() { InitializeComponent(); } </span><span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">void</span> button1_Click(<span style="color: rgba(0, 0, 255, 1)">object</span><span style="color: rgba(0, 0, 0, 1)"> sender, EventArgs e) { </span><span style="color: rgba(0, 0, 255, 1)">if</span> (MyFunc != <span style="color: rgba(0, 0, 255, 1)">null</span><span style="color: rgba(0, 0, 0, 1)">) { MyFunc(); } } }</span></pre>
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有些时候委托绑定的方法比较简单,而且在代码中可能只是用一次
-> 如果不用定义,直接写一个表达式或者一个赋值操作就可以完成这个功能就好了
-> 匿名方法
-> 语法:
委托类型 委托名 = delegate(参数列表) { /* 方法体 */ };
2、 SumHandler sum = (n1, n2) => n1 + n2;
Lambda表达式
参数 => 方法体
=> goes to
参数类型在不冲突的情况下可以省略
如果参数只有一个,可以使用
e => ...
没有参数的时候,可以使用
() => ...
方法体如果只有一句话,省略{}
方法体如果只有一句话,并且有返回值,可以省略return
---------------------------------------------------------------
与函数指针相比,delegate有许多函数指针不具备的优点。首先,函数指针只能指向静态函数,而delegate既可以引用静态函数,又可以引用非静态成员函数。
委托对象可使用 "+" 运算符进行合并。一个合并委托调用它所合并的两个委托。只有相同类型的委托可被合并。"-" 运算符可用于从合并的委托中移除组件委托。
使用委托的这个有用的特点,您可以创建一个委托被调用时要调用的方法的调用列表。这被称为委托的 多播(multicasting),也叫组播。
调用(invoke)委托,相当于调用委托所绑定的方法,一个委托可以绑定多个方法,使用"+="就可以向委托中添加新的方法,使用"-="可以从委托中删除方法
利用鸿门宴解释委托与事件:http://www.cnblogs.com/yinqixin/p/5056307.html
结合delegate的实现,我们可以将自定义事件的实现归结为以下几步:
1.定义delegate对象类型,它有两个参数,第一个参数是事件发送者对象,第二个参数是事件参数类对象。
2.定义事件参数类,此类应当从System.EventArgs类派生。如果事件不带参数,这一步可以省略。
3.定义事件处理方法,它应当与delegate对象具有相同的参数和返回值类型。
4. 用event关键字定义事件对象,它同时也是一个delegate对象。
5.用+=操作符添加事件到事件队列中(-=操作符能够将事件从队列中删除)。
6.在需要触发事件的地方用调用delegate的方式写事件触发方法。一般来说,此方法应为protected访问限制,既不能以public方式调用,但可以被子类继承。名字是OnEventName。
7. 在适当的地方调用事件触发方法触发事件。下面是一个简单的例子:
using System; public class EventTest { // 步骤1,定义delegate对象 public delegate void MyEventHandler(object sender, System.EventArgs e); // 步骤2省略 public class MyEventCls { // 步骤3,定义事件处理方法,它与delegate对象具有相同的参数和返回值类// 型 public void MyEventFunc(object sender, System.EventArgs e) { Console.WriteLine("My event is ok!"); } } // 步骤4,用event关键字定义事件对象 private event MyEventHandler myevent; private MyEventCls myecls; public EventTest() { myecls = new MyEventCls(); // 步骤5,用+=操作符将事件添加到队列中 this.myevent += new MyEventHandler(myecls.MyEventFunc); } // 步骤6,以调用delegate的方式写事件触发函数 protected void OnMyEvent(System.EventArgs e) { if(myevent != null) myevent(this, e); } public void RaiseEvent() { EventArgs e = new EventArgs(); // 步骤7,触发事件 OnMyEvent(e); } public static void Main() { EventTest et = new EventTest(); Console.Write("Please input ''a'':"); string s = Console.ReadLine(); if(s == "a") { et.RaiseEvent(); } else { Console.WriteLine("Error"); } } }
using System; using System.Text; using System.Data;namespace Class1
{
//定义事件引发时,需要传的参数
class NewMailEventArgs:EventArgs
{
private readonly string m_from;
private readonly string m_to;
private readonly string m_subject;
public NewMailEventArgs(string from, string to, string subject)
{
m_from = from;
m_to = to;
m_subject = subject;
}
public string From
{
get{return m_from;}
}
public string To
{
get{return m_to;}
}
public string Subject
{
get{return m_subject;}
}} //提供一个方法,引发事件 public void SimulateNewMail(string from, string to, string subject) { NewMailEventArgs e = new NewMailEventArgs(from,to,subject); OnNewMail(e); } }} </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">事件所用的委托(链表)</span> <span style="color: rgba(0, 0, 255, 1)">delegate</span> <span style="color: rgba(0, 0, 255, 1)">void</span> NewMailEventHandler(<span style="color: rgba(0, 0, 255, 1)">object</span><span style="color: rgba(0, 0, 0, 1)"> sender, NewMailEventArgs e); </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">提供事件的类</span> <span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)"> MailManager { </span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">event</span><span style="color: rgba(0, 0, 0, 1)"> NewMailEventHandler NewMail; </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">通知已订阅事件的对象</span> <span style="color: rgba(0, 0, 255, 1)">protected</span> <span style="color: rgba(0, 0, 255, 1)">virtual</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> OnNewMail(NewMailEventArgs e) { NewMailEventHandler temp </span>= NewMail; <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">MulticastDelegate一个委托链表 </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">通知所有已订阅事件的对象</span> <span style="color: rgba(0, 0, 255, 1)">if</span>(temp != <span style="color: rgba(0, 0, 255, 1)">null</span><span style="color: rgba(0, 0, 0, 1)">) temp(</span><span style="color: rgba(0, 0, 255, 1)">this</span>,e); <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">通过事件NewMail(一种特殊的委托)逐一回调客户端的方法</span>
</span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">使用事件</span> <span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)"> Fax { </span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Fax(MailManager mm) { </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">Subscribe </span> mm.NewMail += <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> NewMailEventHandler(Fax_NewMail); } </span><span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">void</span> Fax_NewMail(<span style="color: rgba(0, 0, 255, 1)">object</span><span style="color: rgba(0, 0, 0, 1)"> sender, NewMailEventArgs e) { Console.WriteLine(</span><span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">Message arrived at Fax...</span><span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(0, 0, 0, 1)">); Console.WriteLine(</span><span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">From={0}, To={1}, Subject='{2}'</span><span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(0, 0, 0, 1)">,e.From,e.To,e.Subject); } </span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> Unregister(MailManager mm) { mm.NewMail </span>-= <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> NewMailEventHandler(Fax_NewMail); } } </span><span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)"> Print { </span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Print(MailManager mm) { </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">Subscribe ,在mm.NewMail的委托链表中加入Print_NewMail方法</span> mm.NewMail += <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> NewMailEventHandler(Print_NewMail); } </span><span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">void</span> Print_NewMail(<span style="color: rgba(0, 0, 255, 1)">object</span><span style="color: rgba(0, 0, 0, 1)"> sender, NewMailEventArgs e) { Console.WriteLine(</span><span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">Message arrived at Print...</span><span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(0, 0, 0, 1)">); Console.WriteLine(</span><span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">From={0}, To={1}, Subject='{2}'</span><span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(0, 0, 0, 1)">,e.From,e.To,e.Subject); } </span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> Unregister(MailManager mm) { mm.NewMail </span>-= <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> NewMailEventHandler(Print_NewMail); } } </span><span style="color: rgba(0, 0, 255, 1)">class</span><span style="color: rgba(0, 0, 0, 1)"> ExcelProgram { [STAThread] </span><span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">void</span> Main(<span style="color: rgba(0, 0, 255, 1)">string</span><span style="color: rgba(0, 0, 0, 1)">[] args) { MailManager mm </span>= <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> MailManager(); </span><span style="color: rgba(0, 0, 255, 1)">if</span>(<span style="color: rgba(0, 0, 255, 1)">true</span><span style="color: rgba(0, 0, 0, 1)">) { Fax fax </span>= <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> Fax(mm); Print prt </span>= <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> Print(mm); } mm.SimulateNewMail(</span><span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">Anco</span><span style="color: rgba(128, 0, 0, 1)">"</span>,<span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">Jerry</span><span style="color: rgba(128, 0, 0, 1)">"</span>,<span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(128, 0, 0, 1)">Event test</span><span style="color: rgba(128, 0, 0, 1)">"</span><span style="color: rgba(0, 0, 0, 1)">); Console.ReadLine(); } }
}
ref和out的区别在C# 中,既可以通过值也可以通过引用传递参数。通过引用传递参数允许函数成员更改参数的值,并保持该更改。若要通过引用传递参数, 可使用ref或out关键字。ref和out这两个关键字都能够提供相似的功效,其作用也很像C中的指针变量。它们的区别是:
1、使用ref型参数时,传入的参数必须先被初始化。对out而言,必须在方法中对其完成初始化。
2、使用ref和out时,在方法的参数和执行方法时,都要加Ref或Out关键字。以满足匹配。
3、out适合用在需要retrun多个返回值的地方,而ref则用在需要被调用的方法修改调用者的引用的时候。
注:在C#中,方法的参数传递有四种类型:传值(by value),传址(by reference),输出参数(by output),数组参数(by array)。传值参数无需额外的修饰符,传址参数需要修饰符ref,输出参数需要修饰符out,数组参数需要修饰符params。传值参数在方法调用过程中如果改变了参数的值,那么传入方法的参数在方法调用完成以后并不因此而改变,而是保留原来传入时的值。传址参数恰恰相反,如果方法调用过程改变了参数的值,那么传入方法的参数在调用完成以后也随之改变。实际上从名称上我们可以清楚地看出两者的含义--传值参数传递的是调用参数的一份拷贝,而传址参数传递的是调用参数的内存地址,该参数在方法内外指向的是同一个存储位置。
方法参数上的 ref 方法参数关键字使方法引用传递到方法的同一个变量。当控制传递回调用方法时,在方法中对参数所做的任何更改都将反映在该变量中。
若要使用 ref 参数,必须将参数作为 ref 参数显式传递到方法。ref 参数的值被传递到 ref 参数。
传递到 ref 参数的参数必须最先初始化。将此方法与 out 参数相比,后者的参数在传递到 out 参数之前不必显式初始化。
属性不是变量,不能作为 ref 参数传递。
如果两种方法的声明仅在它们对 ref 的使用方面不同,则将出现重载。但是,无法定义仅在 ref 和 out 方面不同的重载。
out
方法参数上的 out 方法参数关键字使方法引用传递到方法的同一个变量。当控制传递回调用方法时,在方法中对参数所做的任何更改都将反映在该变量中。
当希望方法返回多个值时,声明 out 方法非常有用。使用 out 参数的方法仍然可以返回一个值。一个方法可以有一个以上的 out 参数。
若要使用 out 参数,必须将参数作为 out 参数显式传递到方法。out 参数的值不会传递到 out 参数。
不必初始化作为 out 参数传递的变量。然而,必须在方法返回之前为 out 参数赋值。
属性不是变量,不能作为 out 参数传递。