[讀書筆記]多播委託

　　委託也可以包含多個方法，這種委託稱為多播委託。如果調用多播委託，就可以按順序連續調用多個方法。為此，委託的簽名就必須返回void.否則，就只能得到委託調用的最後一個方法的結果。

/* * Created by SharpDevelop. * User: Herbert * Date: 2010-3-20 * Time: 23:11 *  * To change this template use Tools | Options | Coding | Edit Standard Headers. */using System;namespace MulticastDelegate{delegate void DoubleOp(double value);class MathOperations{public static void MultiplyByTwo(double value){double result = value*2;Console.WriteLine("Multiply by 2: {0} gives {1}", value, result);}public static void Square(double value){double result = value*value;Console.WriteLine("Squaring: {0} gives {1}", value, result);}}class Program{public static void Main(string[] args){DoubleOp operations = MathOperations.MultiplyByTwo;operations += MathOperations.Square;ProcessAndDisplayNmber(operations, 2.0);ProcessAndDisplayNmber(operations, 7.94);ProcessAndDisplayNmber(operations, 1.414);Console.Write("Press any key to continue . . . ");Console.ReadKey(true);}static void ProcessAndDisplayNmber(DoubleOp action, double valueToProcess){Console.WriteLine();Console.WriteLine("ProcessAndDisplayNumber called with value = {0}", valueToProcess);action(valueToProcess);}}}

 

下面的code

DoubleOp operations = MathOperations.MultiplyByTwo;operations += MathOperations.Square;

 

等價於：

DoubleOp operation1 = MathOperations.MultipleByTow;DoubleOp operation2 = MathOperation.Square;DoubleOp operations = operation1 + operation2;