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：

  

/*
  Example12_1.cs illustrates the use of a delegate
 */

 using System;


// declare the DelegateCalculation delegate class
public delegate double DelegateCalculation(
  double acceleration, double time
);


// declare the MotionCalculations class
public class MotionCalculations
{

  // FinalSpeed() calculates the final speed
  public static double FinalSpeed(
    double acceleration, double time
  )
  {
    double finalSpeed = acceleration * time;
    return finalSpeed;
  }

  // Distance() calculates the distance traveled
  public static double Distance(
    double acceleration, double time
  )
  {
    double distance = acceleration * Math.Pow(time, 2) / 2;
    return distance;
  }

}


class Example12_1
{

  public static void Main()
  {

    // declare and initialize the acceleration and time
    double acceleration = 10;  // meters per second per second
    double time = 5;  // seconds
    Console.WriteLine("acceleration = " + acceleration +
      " meters per second per second");
    Console.WriteLine("time = " + time + " seconds");

    // create a delegate object that calls
    // MotionCalculations.FinalSpeed
    DelegateCalculation myDelegateCalculation =
      new DelegateCalculation(MotionCalculations.FinalSpeed);

    // calculate and display the final speed
    double finalSpeed = myDelegateCalculation(acceleration, time);
    Console.WriteLine("finalSpeed = " + finalSpeed +
      " meters per second");

    // set the delegate method to MotionCalculations.Distance
    myDelegateCalculation =
      new DelegateCalculation(MotionCalculations.Distance);

    // calculate and display the distance traveled
    double distance = myDelegateCalculation(acceleration, time);
    Console.WriteLine("distance = " + distance + " meters");

  }

}