委派

委托就像一个函数的指针，在程序运行时可以使用它们来调用不同的函数。委托存储方法名，以及返回值类型和参数列表。一个委派有两个部分：委派类和类的委派对象。

定义委派类，如 public delegate double DelegateCalculation(

　　　　double acceleration ,double time

);

然后可以创建一个委派对象

DelegateCalculation myDelegateCalculation =
new DelegateCalculation(MotionCalculations.FinalSpeed);

例如：

 1 /*
 2   Example12_1.cs illustrates the use of a delegate
 3  */
 4 
 5  using System;
 6 
 7 
 8 // declare the DelegateCalculation delegate class
 9 public delegate double DelegateCalculation(
10   double acceleration, double time
11 );
12 
13 
14 // declare the MotionCalculations class
15 public class MotionCalculations
16 {
17 
18   // FinalSpeed() calculates the final speed
19   public static double FinalSpeed(
20     double acceleration, double time
21   )
22   {
23     double finalSpeed = acceleration * time;
24     return finalSpeed;
25   }
26 
27   // Distance() calculates the distance traveled
28   public static double Distance(
29     double acceleration, double time
30   )
31   {
32     double distance = acceleration * Math.Pow(time, 2) / 2;
33     return distance;
34   }
35 
36 }
37 
38 
39 class Example12_1
40 {
41 
42   public static void Main()
43   {
44 
45     // declare and initialize the acceleration and time
46     double acceleration = 10;  // meters per second per second
47     double time = 5;  // seconds
48     Console.WriteLine("acceleration = " + acceleration +
49       " meters per second per second");
50     Console.WriteLine("time = " + time + " seconds");
51 
52     // create a delegate object that calls
53     // MotionCalculations.FinalSpeed
54     DelegateCalculation myDelegateCalculation =
55       new DelegateCalculation(MotionCalculations.FinalSpeed);
56 
57     // calculate and display the final speed
58     double finalSpeed = myDelegateCalculation(acceleration, time);
59     Console.WriteLine("finalSpeed = " + finalSpeed +
60       " meters per second");
61 
62     // set the delegate method to MotionCalculations.Distance
63     myDelegateCalculation =
64       new DelegateCalculation(MotionCalculations.Distance);
65 
66     // calculate and display the distance traveled
67     double distance = myDelegateCalculation(acceleration, time);
68     Console.WriteLine("distance = " + distance + " meters");
69 
70   }
71 
72 }