最简单的委托示例：
1 // 该委托可以指向任何传入两个整数并返回一个整数的方法
2 public delegate int BinaryOp( int x, int y );
3 public class SimpleMath
4 {
5 public int Add( int x, int y )
6 { return x + y; }
7 public int Subtract( int x, int y )
8 { return x - y; }
9 public static int SquareNumber( int a )
10 { return a * a; }
11 }
12 class Program
13 {
14 static void Main( string[] args )
15 {
16 Console.WriteLine("***** Simple Delegate Example *****\n");
17
18 SimpleMath m = new SimpleMath();
19
20 BinaryOp b = new BinaryOp(m.Add);
21 DisplayDelegateInfo(b);
22
23 Console.WriteLine("10 + 10 is {0}", b(10, 10));
24
25 Console.ReadLine();
26 }
27 static void DisplayDelegateInfo( Delegate delObj )
28 {
29 foreach (Delegate d in delObj.GetInvocationList())
30 {
31 Console.WriteLine("Method Name: {0}", d.Method);
32 Console.WriteLine("Type Name: {0}", d.Target);
33 }
34 }
35 }
支持多路广播的委托示例：
1 /*
2 * 2015.5
3 * Car.cs
4 */
5 using System;
6 using System.Collections.Generic;
7 using System.Linq;
8 using System.Text;
9 using System.Threading.Tasks;
10
11 namespace CarDelegate
12 {
13 public class Car
14 {
15 // 内部状态数据
16 public int CurrentSpeed { get; set; }
17 public int MaxSpeed { get; set; }
18 public string PetName { get; set; }
19 private bool carIsDead = false;
20
21 // 构造函数
22 public Car() { MaxSpeed = 180; }
23 public Car( string name, int maxSp, int currSp )
24 {
25 CurrentSpeed = currSp;
26 MaxSpeed = maxSp;
27 PetName = name;
28 }
29
30 // 定义委托类型
31 public delegate void CarEngineHandler( string msgForCaller );
32
33 // 定义每个委托类型的成员变量
34 private CarEngineHandler listOfHandlers;
35
36 // 添加注册函数
37 public void RegisterWithCarEngine( CarEngineHandler methodToCall )
38 { // 给每个委托对象添加多个方法
39 // 支持多路广播，可以使用 +=操作符，或直接调用Delegate.Combine()
40
41 // listOfHandlers += methodToCall;
42
43 if (listOfHandlers == null)
44 listOfHandlers = methodToCall;
45 else
46 Delegate.Combine(listOfHandlers, methodToCall);
47 }
48
49 public void UnRegisterWithCarEngine( CarEngineHandler methodToCall )
50 { // 从委托的调用列表移除成员, 也可调用 Delegate.Remove()
51
52 listOfHandlers -= methodToCall;
53 }
54
55 public void Accelerate( int delta )
56 {
57 if (carIsDead)
58 {
59 if (listOfHandlers != null)
60 listOfHandlers("Sorry, this car is dead...");
61 }
62 else
63 {
64 CurrentSpeed += delta;
65 if (10 == (MaxSpeed - CurrentSpeed)
66 && listOfHandlers != null)
67 {
68 listOfHandlers("Careful buddy!");
69 }
70 if (CurrentSpeed >= MaxSpeed)
71 carIsDead = true;
72 else
73 Console.WriteLine("CurrentSpeed = {0}", CurrentSpeed);
74 }
75 }
76 }
77 }
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6
7 namespace CarDelegate
8 {
9 class Program
10 {
11 static void Main( string[] args )
12 {
13 Console.WriteLine("***** Delegates as event enablers *****\n");
14
15 Car c1 = new Car("BMW", 100, 10);
16
17 // 先绑定委托对象，稍后再注销
18 Car.CarEngineHandler handler2 = new Car.CarEngineHandler(OnCarEngineEvent2);
19 c1.RegisterWithCarEngine(handler2);
20
21 Console.WriteLine("***** Speeding up 1*****");
22 for (int i = 0; i < 6; i++)
23 c1.Accelerate(20);
24
25 c1.UnRegisterWithCarEngine(handler2);
26
27 // 注销上一种方法，注册另一种方法
28 // 观察到两种方法的输出不一样
29 c1.RegisterWithCarEngine(new Car.CarEngineHandler(OnCarEngineEvent));
30 Console.WriteLine("***** Speeding up 2*****");
31 for (int i = 0; i < 6; i++)
32 c1.Accelerate(20);
33
34 Console.ReadLine();
35 }
36
37 public static void OnCarEngineEvent( string msg )
38 {
39 Console.WriteLine("\n***** Message From Car Object *****");
40 Console.WriteLine("=> {0}", msg);
41 Console.WriteLine("***********************************\n");
42 }
43
44 public static void OnCarEngineEvent2( string msg )
45 {
46 Console.WriteLine("=> {0}", msg.ToUpper());
47 }
48 }
49 }
泛型Action<>和Func<>委托示例：
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6
7 namespace ActionAndFuncDelegates
8 {
9 class Program
10 {
11 static void Main(string[] args)
12 {
13 Console.WriteLine("***** Fun with Action and Func *****\n");
14
15 // 使用泛型 Action<> 委托来指向DisplayMessage， Action<>可以指向多至16个参数
16 Action<string, ConsoleColor, int> actionTarget =
17 new Action<string, ConsoleColor, int>(DisplayMessage);
18
19 actionTarget("Action Message!", ConsoleColor.Green, 5);
20
21 // 使用泛型 Func<> 委托
22 Func<int, int, int> funcTarget = new Func<int, int, int>(Add);
23 int result = funcTarget.Invoke(40, 40);
24 Console.WriteLine("40 + 40 = {0}", result);
25
26 Func<int, int, string> funcTarget2 = new Func<int, int, string>(SumToString);
27 string sum = funcTarget2(90, 300);
28 Console.WriteLine(sum);
29
30 Console.ReadLine();
31 }
32
33 static void DisplayMessage(string msg, ConsoleColor txtColor, int printCount)
34 {
35 // 设置命令行文本颜色
36 ConsoleColor previous = Console.ForegroundColor;
37 Console.ForegroundColor = txtColor;
38
39 for (int i = 0; i < printCount; i++)
40 {
41 Console.WriteLine(msg);
42 }
43 // 重置颜色
44 Console.ForegroundColor = previous;
45 }
46
47 static int Add(int x, int y)
48 {
49 return x + y;
50 }
51
52 static string SumToString(int x, int y)
53 {
54 return (x + y).ToString();
55 }
56 }
57 }
在事件注册时直接将一个委托与一段代码相关联称为匿名方法。使用 +=语法处理事件时被内联定义。
如：
Car c1 = new Car("BMW", 100, 10);
c1.AboutToBlow += delegate(object sender, CarEventArgs e)
{
aboutToBlowCounter++;
Console.WriteLine("Message from Car: {0}", e.msg);
};
C#的Lambda 表达式都使用 Lambda 运算符 =>，该运算符读为“goes to”。语法如下：
形参列表=>函数体
函数体多于一条语句的可用大括号括起。
Lambda 表达式可以用于任何匿名方法或者强类型委托可以应用的场合，而且比匿名方法更节省编码时间。其实编译器只是把表达式编译为使用委托Predicate<T>的标准匿名方法而已。
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6
7 namespace LambdaExpressionsMultipleParams
8 {
9 public class SimpleMath
10 {
11 // 多个参数
12 public delegate void MathMessage( string msg, int result );
13 private MathMessage mmDelegate;
14
15 public void SetMathHandler( MathMessage target )
16 { mmDelegate = target; }
17
18 public void Add( int x, int y )
19 {
20 if (mmDelegate != null)
21 mmDelegate.Invoke("Adding has completed!", x + y);
22 }
23 }
24
25 class Program
26 {
27 static void Main( string[] args )
28 {
29 // 使用Lambda表达式注册委托
30 SimpleMath m = new SimpleMath();
31 m.SetMathHandler(( msg, result ) =>
32 { Console.WriteLine("Message: {0}, Result: {1}", msg, result); });
33
34 // 执行Lambda表达式
35 m.Add(10, 10);
36 Console.ReadLine();
37 }
38 }
39 }
时间： 2024-08-05 09:40:00