C#方法（函数）

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

 namespace _04.方法_函数_
 {
     class Program
     {
         static void Main(string[] args)
         {
             //求2个整数的最大值
             //int max = Program.GetMax(1, 2);
             //Console.WriteLine("最大值为{0}", max);
             //Console.ReadKey();

             //判断闰年
             //bool b = IsRun(2100);
             //Console.WriteLine(b);
             //Console.ReadKey();

             //输入数字跳出循环，否则继续
             //Console.WriteLine("请输入一个数字");
             //string input = Console.ReadLine();
             //int number = GetNum(input);
             //Console.WriteLine(number);
             //Console.ReadKey();

             //输入yes\no，否则继续
             //Console.WriteLine("请输入yes\no");
             //string input = Console.ReadLine();
             //string result = IsYesOrNo(input);
             //Console.WriteLine(result);
             //Console.ReadKey();

             //求数组的和
             //int[] nums = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
             //int result = GetSum(nums);
             //Console.WriteLine(result);
             //Console.ReadKey();

             //求数组的最大、最小、总和、平均值
             //int[] nums = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
             //int max = 0;
             //int min = 0;
             //int sum = 0;
             //int avg = 0;
             //Test(nums,out max,out min,out sum,out avg);
             //Console.WriteLine(max);
             //Console.WriteLine(min);
             //Console.WriteLine(sum);
             //Console.WriteLine(avg);
             //Console.ReadKey();

             //判断登录条件
             //Console.WriteLine("username");
             //string username = Console.ReadLine();
             //Console.WriteLine("password");
             //string password = Console.ReadLine();
             //string msg;
             //bool b = IsLogin(username, password, out msg);
             //Console.WriteLine(b);
             //Console.WriteLine(msg);
             //Console.ReadKey();

             //交换2个int型的整数
             //int n1 = 10;
             //int n2 = 20;
             //Change(ref n1, ref n2);
             //Console.WriteLine("{0}, {1}", n1, n2);
             //Console.ReadKey();

             //输入姓名、学号、成绩，计算总成绩
             ////int[] s = { 99, 99, 99 };
             //Score("张三", 101, 99, 99, 99);
             //Console.ReadKey();

             //方法递归
             //TellStory();
             //Console.ReadKey();

             //方法综合练习6.7.12

             //求一个字符串数组中最长的元素
             //string[] names = { "马云", "罗振宇", "科比布莱恩特", "扎克伯格"};
             //Console.WriteLine(GetLongStr(names));
             //Console.ReadKey();
         }

         #region 2个数的最大值
         /// <summary>
         /// 求2个数的最大值
         /// </summary>
         /// <param name="n1">第一个整数</param>
         /// <param name="n2">第二个整数</param>
         /// <returns>返回最大值</returns>
         public static int GetMax(int n1, int n2)
         {
             return n1 > n2 ? n1 : n2;
         }
         #endregion

         #region 判断闰年
         /// <summary>
         /// 判断给出的年份是否为闰年
         /// </summary>
         /// <param name="year">年份</param>
         /// <returns>bool</returns>
         public static bool IsRun(int year)
         {
             bool b = (year %  == ) || (year %  ==  && year %  != );
             return b;
         }
         #endregion

         #region 判断用户的输入是否为数字
         /// <summary>
         /// 判断用户的输入是否为数字
         /// </summary>
         /// <param name="s"></param>
         /// <returns></returns>
         public static int GetNum(string s)
         {
             while (true)
             {
                 try
                 {
                     int number = Convert.ToInt32(s);
                     return number;
                 }
                 catch
                 {
                     Console.WriteLine("输入有误");
                     s = Console.ReadLine();
                 }
             }
         }
         #endregion

         #region yes\no跳出循环
         /// <summary>
         /// 输入yes\no
         /// </summary>
         /// <param name="input"></param>
         /// <returns></returns>
         public static string IsYesOrNo(string input)
         {
             while (true)
             {
                 if (input == "yes" || input == "no")
                 {
                     return input;
                 }
                 else
                 {
                     Console.WriteLine("请重新输入");
                     input = Console.ReadLine();
                 }
             }
         }
         #endregion

         #region 求数组的和
         /// <summary>
         /// 求数组的和
         /// </summary>
         /// <param name="numbers"></param>
         /// <returns></returns>
         public static int GetSum(int[] numbers)
         {
             int sum = ;
             for (int i = ; i < numbers.Length; i++)
             {
                 sum += numbers[i];
             }
             return sum;
         }
         #endregion

         #region 返回数组的最大、最小、总和、平均值
         /// <summary>
         /// 返回数组的最大、最小、总和、平均值
         /// </summary>
         /// <param name="nums">数组</param>
         /// <param name="max">多于反悔的最大值</param>
         /// <param name="min">多于反悔的最小值</param>
         /// <param name="sum">多于反悔的总和</param>
         /// <param name="avg">多于反悔的平均值</param>
         public static void Test(int[] nums, out int max, out int min, out int sum, out int avg)
         {
             max = nums[];
             min = nums[];
             sum = ;
             for (int i = ; i < nums.Length; i++)
             {
                 if (nums[i] > max)
                 {
                     max = nums[i];
                 }
                 if (nums[i] < min)
                 {
                     min = nums[i];
                 }
                 sum += nums[i];
             }
             avg = sum / nums.Length;
         }
         #endregion

         #region 判断登录条件
         /// <summary>
         /// 判断登录条件
         /// </summary>
         /// <param name="uid">username</param>
         /// <param name="pwd">password</param>
         /// <param name="msg">错误信息</param>
         /// <returns></returns>
         public static bool IsLogin(string uid, string pwd, out string msg)
         {
             if (uid == "admin" && pwd == "")
             {
                 msg = "登录成功";
                 return true;
             }
             else if (uid == "admin")
             {
                 msg = "密码错误";
                 return false;
             }
             else if (pwd == "")
             {
                 msg = "用户名错误";
                 return false;
             }
             else
             {
                 msg = "全部错误";
                 return false;
             }
         }
         #endregion

         #region 交换2个int型的整数
         /// <summary>
         /// 交换2个int型的整数
         /// </summary>
         /// <param name="n1">n1</param>
         /// <param name="n2">n2</param>
         public static void Change(ref int n1, ref int n2)
         {
             int temp = n1;
             n1 = n2;
             n2 = temp;
         }
         #endregion

         #region 输入姓名、学号、成绩，计算总成绩
         /// <summary>
         /// 输入姓名、学号、成绩，计算总成绩
         /// </summary>
         /// <param name="name">姓名</param>
         /// <param name="id">学号</param>
         /// <param name="score">成绩数组</param>
         public static void Score(string name, int id, params int[] score)
         {
             int sum = ;
             for (int i = ; i < score.Length; i++)
             {
                 sum += score[i];
             }
             Console.WriteLine("{0}的总成绩为{1}，学号{2}", name, sum, id);
         }
         #endregion

         #region 方法递归
         /// <summary>
         /// 方法递归
         /// </summary>
         public static int i = ;
         public static void TellStory()
         {
             Console.WriteLine("从前有座庙");
             Console.WriteLine("庙里有个老和尚和小和尚");
             Console.WriteLine("有一天，老和尚对小和尚说：");
             i++;
             if (i > )
             {
                 return;
             }
             TellStory();
         }
         #endregion

         #region 计算字符串数组中的最大值
         /// <summary>
         /// 计算字符串数组中的最大值
         /// </summary>
         /// <param name="s">数组</param>
         /// <returns>最大值</returns>
         public static string GetLongStr(string[] s)
         {
             string max = s[];
             for (int i = ; i < s.Length; i++)
             {
                 if (s[i].Length > max.Length)
                 {
                     max = s[i];
                 }
             }
             return max;
         }
         #endregion
     }
 }