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C#—委托分析
1.简单委托示例
using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace SimpleTest { class Program { private delegate string GetAString(); //声明委托 static void Main(string[] args) { int x = 40; GetAString delegateString = new GetAString(x.ToString); //委托接受一个参数的构造函数 GetAString delegateString1 = x.ToString; //将方法的地址赋值给委托变量 Tostring()是字符串对象 Console.WriteLine("string is {0}",delegateString()); Console.WriteLine("string1 is {0}", delegateString1()); } } }
输出结果
2.委托数组实现多播委托(调用多个方法) 包括func<T>委托方式
操作类(MathOperation)
using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace SimpleTest1 { class MathOperation { public static double MultiplyByTwo(double value) { return value * 2; } public static double Square(double value) { return value * value; } } }
测试类
using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace SimpleTest1 { class Program { delegate double DoubleOP(double value); //声明委托 //将委托传递给方法 //委托作为第一个参数传递 private static void ProcessAndDisplayNumber(DoubleOP action,double value) { double result = action(value); // Console.WriteLine("Value is {0},result of operation is {1}",value,result); } //利用Func<T>泛型实现委托 private static void ProcessAndDisplayNumber(Func<double, double> action, double value) { double result = action(value); Console.WriteLine("Value is {0},result of operation is {1}", value, result); } static void Main(string[] args) { //方式一 //DoubleOP[] operations = // 实例化一个委托的数组,可以在循环中调用不同的方法 //{ // MathOperation.MultiplyByTwo, // MathOperation.Square //}; //方式二 Func<double, double>[] operations = //Func<T>允许调用带返回类型的方法 { MathOperation.MultiplyByTwo, MathOperation.Square }; /* * i=0的时候,即operations[0]委托的实例为 MathOperation.MultiplyByTwo, * 调用ProcessAndDisplayNumber(operations[0],2.0)后 * double result = action(value); // action(value)相当于调用MathOperation.MultiplyByTwo(value) * operations[i] 委托表示的方法,operations[i](2.0) 调用委托的商品 */ for (int i = 0; i < operations.Length; i++) { Console.WriteLine("Using operations [{0}]:", i); ProcessAndDisplayNumber(operations[i], 2.0); ProcessAndDisplayNumber(operations[i], 7.84); ProcessAndDisplayNumber(operations[i], 1.414); Console.WriteLine(); } } } }
输出结果
3.Action<T>实现多播委托改上上述测试样例
操作类(MathOperation)
using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace Multicastdelegate { class MathOperations { public static void MultiplyByTwo(double value) { double result = value * 2; Console.WriteLine("[{0}]Multiply by 2 = [{1}]:",value,result); } public static void Square(double value) { double result = value * value; Console.WriteLine("[{0}]Square = [{1}]",value,result); } } }
测试类:
using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace Multicastdelegate { class Program { /// <summary> /// 多播委托方式 /// </summary> /// <param name="action"></param> /// <param name="value"></param> public static void ProcessAndDisplayNumber(Action<double> action,double value) { Console.WriteLine("ProcessAndDisplayNumber called with value=http://www.mamicode.com/{0}",value); action(value); } static void Main(string[] args) { Action<double> operations = MathOperations.MultiplyByTwo; operations+= MathOperations.Square; //+=向委托中添加方法 ProcessAndDisplayNumber(operations,2.0); ProcessAndDisplayNumber(operations, 4.0); } } }
输出结果:
4.对象排序的委托(冒泡排序)
冒泡算法类(BubbleSorter)
using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace BubbleSort { /// <summary> /// 冒泡排序 /// </summary> class BubbleSorter { /// <summary> /// comparison必须引用一个方法,该方法带有两个参数,如果第一个参数“小于”第二个参数返回true /// </summary> /// <typeparam name="T"></typeparam> /// <param name="sortArray"></param> /// <param name="comparison"></param> static public void Sort<T>(IList<T> sortArray, Func<T, T, bool> comparison) { bool swapped = true; do { swapped = false; for (int i = 0; i < sortArray.Count - 1; i++) { if (comparison(sortArray[i + 1], sortArray[i])) { T temp = sortArray[i]; sortArray[i] = sortArray[i + 1]; sortArray[i + 1] = temp; swapped = true; } } } while (swapped); } } }
职工信息类(Employee)
using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace BubbleSort { class Employee { public string Name { get; set; } public decimal Salary { get; set; } public override string ToString() { return string.Format("{0},{1:C}", Name, Salary); } public Employee(string name, decimal salary) { this.Name = name; this.Salary = salary; } /// <summary> /// 为了匹配冒泡排序的Func<T, T, bool> comparison必须定义如下方法 /// </summary> /// <param name="e1"></param> /// <param name="e2"></param> /// <returns></returns> public static bool CompareSalary(Employee e1, Employee e2) { return e1.Salary < e2.Salary; } } }
测试类
using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace BubbleSort { class Program { static void Main(string[] args) { Employee[] employees = { new Employee("小张", 2000), new Employee("小王", 3000), new Employee("小李", 4000), new Employee("小赵", 2500) }; BubbleSorter.Sort(employees, Employee.CompareSalary); //利用委托对对象排序 foreach (var employee in employees) { Console.WriteLine(employee); } } } }
输出结果:
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