C#中的委托(二)

一、Action<T>和Func<T>委托

     除了上篇描述的为每个参数和返回类型定义一个新委托类型之外,还可以使用Action<T>和Func<T>委托。通过T的标示,我们可以知道这是两个泛型委托。

二、Action<T>

     其中Action<T>委托表示引用一个void返回类型的方法。这个委托存在不同的变体,可以传递最多16种不同的参数类型。如:Action<in T1>表示调用带一个参数的方法(返回类型为void),Action<in T1,in T2>表示两个参数,Action<in T1.....in T16>表示16个参数(最多16个);在这就以上篇中数据操作类,加以改造:

    public class MathOperation
    {
        public static void Add(int x, int y)
        {
            int result = x + y;
            Console.WriteLine("x+y={0}", result);
        }

        public static void Reduce(int x, int y)
        {
            int result = x - y;
            Console.WriteLine("x-y={0}", result);
        }

        public static void Process(Action<int, int> action, int x, int y)
        {
            action(x, y);
        }
    }

执行代码:

            Action<int, int>[] operation = { 
                                         MathOperation.Add,
                                         MathOperation.Reduce
                                         };

            for (int i = 0; i < operation.Length; i++)
            {
                Console.WriteLine("执行第{0}个委托方法", i);
                for (int j = 1; j < 10; j++)
                {
                    MathOperation.Process(operation[i], i, j);
                    Thread.Sleep(20);
                }
            }

输出结果:

三、Func<T>

     Func<T>调用带返回类型的方法。与Action<T>类似,Func<T>也定义了不同的变体,至多可以16个参数类型和一个返回类型。Func<out TResult>委托类型可以调用带返回类型且无参的方法,Func<in T,out TResult>表示带有一个参数的方法。我们继续在数据操作类上改造:

    public class MathOperation
    {
        public static int Add(int x, int y)
        {
            int result = x + y;
            return result;
        }

        public static int Reduce(int x, int y)
        {
            int result = x - y;
            return result;
        }

        public static void Process(Func<int, int, int> action, int x, int y)
        {
            int result = action(x, y);
            Console.WriteLine("执行结果为:{0}", result);
        }
    }

执行代码:

            Func<int, int,int>[] operation = { 
                                         MathOperation.Add,
                                         MathOperation.Reduce
                                         };

            for (int i = 0; i < operation.Length; i++)
            {
                Console.WriteLine("执行第{0}个委托方法", i);
                for (int j = 1; j < 10; j++)
                {
                    MathOperation.Process(operation[i], i, j);
                    Thread.Sleep(20);
                }
            }

执行结果:

四、员工工资排序实例

     首先定义一个员工类

    public class Empolyee
    {
        /// <summary>
        /// 姓名
        /// </summary>
        public string Name { get; set; }

        /// <summary>
        /// 工资
        /// </summary>
        public decimal Salary { get; set; }

        public Empolyee(string name, decimal salary)
        {
            this.Name = name;
            this.Salary = salary;
        }

        /// <summary>
        /// 重构
        /// </summary>
        /// <returns></returns>
        public override string ToString()
        {
            return string.Format("{0}的工资为:{1}", Name, Salary);
        }

        /// <summary>
        /// 定义一个比较员工工资的静态方法(用于向通用排序类传值)
        /// </summary>
        /// <param name="e1"></param>
        /// <param name="e2"></param>
        /// <returns></returns>
        public static bool CompareTo(Empolyee e1, Empolyee e2)
        {
            return e1.Salary < e2.Salary;
        }
    }

     然后创建一个排序类:

    public class SortUtil
    {
        public static void Sort<T>(IList<T> arrList, Func<T, T, bool> compare)
        {
            ////冒泡排序
            //for (int i = 0; i < arrList.Count - 1; i++)
            //{
            //    for (int j = i + 1; j < arrList.Count - 1; j++)
            //    {
            //        if (compare(arrList[i], arrList[j]))
            //        {
            //            var temp = arrList[i];
            //            arrList[i] = arrList[j];
            //            arrList[j] = temp;
            //        }
            //    }
            //}

            bool result = true;
            do
            {
                result = false;
                for (var i = 0; i < arrList.Count - 1; i++)
                {
                    if (compare(arrList[i], arrList[i + 1]))
                    {
                        T temp = arrList[i];
                        arrList[i] = arrList[i + 1];
                        arrList[i + 1] = temp;
                        result = true;
                    }
                }
            }
            while (result);

        }
    }

执行代码:

            Empolyee[] list = { 
                              new Empolyee("A",12.3M),
                              new Empolyee("B",12.4M),
                              new Empolyee("C",12.2M),
                              new Empolyee("D",12.5M),
                              new Empolyee("E",12.1M)
                              };

            SortUtil.Sort<Empolyee>(list, Empolyee.CompareTo);

            foreach (var item in list)
            {
                Console.WriteLine(item.ToString());
            }

执行结果:

 

posted @ 2017-05-30 22:38 Rich.W 阅读(...) 评论(...) 编辑 收藏