C#泛型委托

任务：

（1）找出int数组里面最大值的那个元素
（2）找出string数组里面最长的那个元素
（3）找出Person数组里面年龄最大的那个元素的名字

一、下面代码是比较原始的做法

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace GetMaxExample
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] nums = { 1, 2, 3, 4, 5, 6, 7 };
            string[] names = { "张", "李四", "王五明", "zhafdsfdsfds" };
            Person[] persons = { new Person { Age = 12, Name = "小花" }, new Person { Age = 15, Name = "刘伟" }, new Person { Age = 22, Name = "东东" } };

            int maxInt = 0;
            string LengthName = string.Empty;
            Person person = null;
            Console.WriteLine(GetMaxInt(nums, maxInt));
            Console.WriteLine(GetLengthString(names,LengthName));
            Console.WriteLine(GetPersonName(persons,person));


        }
        #region 最原始的方式
        //找出int数组里面最大值的那个元素
        static int GetMaxInt(int[] nums,int max)
        {
            max = nums[0];
            for (int i = 0; i < nums.Length; i++)
            {
                
                if (nums[i]>max)
                {
                    max = nums[i];
                }
            }
            return max;
        }
        //找出string数组里面最长的那个元素
        static string GetLengthString(string[] names,string name)
        {
            name = names[0];
            for (int i = 0; i < names.Length; i++)
            {
                if ((names[i].Length-name.Length)>0)
                {
                    name = names[i];
                }
            }
            return name;
        }
        //找出Person数组里面年龄最大的那个元素的名字
        static string GetPersonName(Person[] persons,Person person)
        {
            person = persons[0];
            for (int i = 0; i < persons.Length; i++)
            {
                if (persons[i].Age>person.Age)
                {
                    person = persons[i];
                }
            }
            return person.Name;
        }
        #endregion

        static object 
    }

    class Person
    {
        public int Age { get; set; }
        public string Name { get; set; }
    }

}

二、统一用Ojbect类型来进行比较（涉及到拆箱和装箱，效率不高）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace _02求数组的最大值
{
    public delegate int DelCompare(object o1, object o2);
    class Program
    {
        static void Main(string[] args)
        {
            object[] nums = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };

            object[] names = { "张三", "李四", "王五", "zhafdsfdsfds" };
            
            object[] pers = { new Person() { Name = "张三", Age = 19 }, new Person() { Name = "李四", Age = 29 } };

            #region 整型数组比较
            DelCompare delComInt = new DelCompare(C1);
            object maxNum = GetMax(nums, delComInt);
            Console.WriteLine((int)maxNum);
            #endregion

            #region 字符串数组比较
            DelCompare delComString = new DelCompare(C2);
            object lengthName = GetMax(names, delComString);
            Console.WriteLine((string)lengthName);
            #endregion

            #region Person数组比较
            //正常使用委托
            DelCompare delComPerson = new DelCompare(C3);
            object maxAgeName = GetMax(pers, delComPerson);
            //匿名函数
            //object maxAgeName = GetMax(pers, delegate(object o1, object o2) { return ((Person)o1).Age - ((Person)o2).Age; });
            //Lambda表达式
            //object maxAgeName = GetMax(pers, (o1, o2) => { return ((Person)o1).Age - ((Person)o2).Age; });
            Console.WriteLine(((Person)maxAgeName).Name);
            #endregion

        }

        static object GetMax(object[] array, DelCompare del)
        {
            object max = array[0];
            for (int i = 0; i < array.Length; i++)
            {
                if (del(max, array[i]) < 0)//需要传进来一个比较的方式
                {
                    max = array[i];
                }
            }
            return max;
        }
        static int C1(object o1, object o2)
        {
            int n1 = (int)o1;
            int n2 = (int)o2;
            return n1 - n2;
        }
        static int C2(object o1, object o2)
        {
            string s1 = (string)o1;
            string s2 = (string)o2;
            return s1.Length - s2.Length;
        }
        static int C3(object o1,object o2)
        {
            Person p1 = (Person)o1;
            Person p2 = (Person)o2;
            return p1.Age - p2.Age;
        }

    }

    class Person
    {
        public string Name { get; set; }
        public int Age { get; set; }
    }

}

三、使用泛型委托和Lambda表达式

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace TDelegateExample
{
    class Program
    {
        public delegate int DelCompare<T>(T T1, T T2);
        static void Main(string[] args)
        {
            int[] nums = { 1, 2, 3, 4, 5, 6, 7, 8,9 };
            string[] names = { "agbaef", "atetq", "tiuqehlasd" };
            Person[] persons = { new Person() { Name = "张三", Age = 19 }, new Person() { Name = "李四", Age = 29 } };
            
            //泛型委托   Lambda表达式
            int numResult = GetMax(nums, (num1, num2) => { return num1 - num2; });
            Console.WriteLine(numResult);

            string stringResult = GetMax(names, (string1, string2) => { return string1.Length - string2.Length; });
            Console.WriteLine(stringResult);

            Person personResult = GetMax(persons, (person1, person2) => { return person1.Age - person2.Age; });
            Console.WriteLine(((Person)personResult).Name);
        }
        static T GetMax<T>(T[] array,DelCompare<T> del)
        {
            T max = array[0];
            for (int i = 0; i < array.Length; i++)
            {
                if (del(max,array[i])<0)
                {
                    max = array[i];
                }
            }
            return max;
        }
    }
    class Person
    {
        public int Age { get; set; }
        public string Name { get; set; }
    }
}