out

每个方法只能有一个返回值，但是你想返回多个值，那就用out。

练习1

class Program
    {
        static void Main(string[] args)
        {
            //分别的提示用户输入用户名和密码
            //你写一个方法来判断用户输入的是否正确
            //返回给用户一个登陆结果，并且还要单独的返回给用户一个登陆信息
            //如果用户名错误，除了返回登陆结果之外，还要返回一个 "用户名错误"
            //“密码错误”
            Console.WriteLine("请输入用户名");
            string userName = Console.ReadLine();
            Console.WriteLine("请输入密码");
            string userPwd = Console.ReadLine();
            string msg;//此处定义一个变量，仅用于接受方法传出来的值，无需初始化。
            bool b = IsLogin(userName, userPwd, out msg);
    <br>　　　　　　  Console.WriteLine("登陆结果：{0}", b); //登陆结果：false
            Console.WriteLine("登陆信息：{0}", msg);//登陆信息：未知错误
            Console.ReadKey();
        }
 
        /// <summary>
        /// 判断登陆是否成功
        /// </summary>
        /// <param name="name">用户名</param>
        /// <param name="pwd">密码</param>
        /// <param name="msg">多余返回的登陆信息</param>
        /// <returns>返回登陆结果</returns>
        public static bool IsLogin(string name, string pwd, out string msg)
        {
            if (name == "admin" && pwd == "888888")
            {
                msg = "登陆成功";
                return true;
            }
            else if (name == "admin")
            {
                msg = "密码错误";
                return false;
            }
            else if (pwd == "888888")
            {
                msg = "用户名错误";
                return false;
            }
            else
            {
                msg = "未知错误";
                return false;
            }
        }
    }

100

101

102

103

104

105

<br>//更复杂的练习<br><br> class Program
    {
        static void Main(string[] args)
        {
            //写一个方法 求一个数组中的最大值、最小值、总和、平均值
            int[] numbers = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
            //将要返回的4个值，放到一个数组中返回
        
            int[] res = GetMaxMinSumAvg(numbers);
            Console.WriteLine("最大值是{0},最小值是{1},总和是{2},平均值是{3}", res[0], res[1], res[2], res[3]);
   
 
            int max1;
            int min1;
            int sum1;
            int avg1;
            bool b;
            string s;
            double d;
            Test(numbers, out max1, out min1, out sum1, out avg1, out b, out s, out d);
 
            Console.WriteLine(max1);
            Console.WriteLine(min1);
            Console.WriteLine(sum1);
            Console.WriteLine(avg1);
            Console.WriteLine(b);
            Console.WriteLine(s);
            Console.WriteLine(d);
            Console.ReadKey();
 
        }
        /// <summary>
        /// 计算一个数组的最大值、最小值、总和、平均值
        /// </summary>
        /// <param name="nums"></param>
        /// <returns></returns>
        public static int[] GetMaxMinSumAvg(int[] nums)
        {
            int[] res = new int[4];
            //定义 res[0] 最大值  res[1]最小值  res[2]总和  res[3]平均值
            res[0] = nums[0];//max
            res[1] = nums[0];//min
            res[2] = 0;//sum
            string name = "孙全";
            bool b = true;
 
            for (int i = 0; i < nums.Length; i++)
            {
                //如果当前循环到的元素比我假定的最大值还大 
                if (nums[i] > res[0])
                {
                    //将当前循环到的元素赋值给我的最大值
                    res[0] = nums[i];
                }
                if (nums[i] < res[1])
                {
                    res[1] = nums[i];
                }
                res[2] += nums[i];
            }
            //平均值
            res[3] = res[2] / nums.Length;
            return res;
 
 
        }
 
 
        /// <summary>
        /// 计算一个整数数组的最大值、最小值、平均值、总和
        /// </summary>
        /// <param name="nums">要求值得数组</param>
        /// <param name="max">多余返回的最大值</param>
        /// <param name="min">多余返回的最小值</param>
        /// <param name="sum">多余返回的总和</param>
        /// <param name="avg">多余返回的平均值</param>
        public static void Test(int[] nums, out int max, out int min, out int sum, out int avg, out bool b, out string s, out double d)
        {
            //out参数要求在方法的内部必须为其赋值
            max = nums[0];
            min = nums[0];
            sum = 0;
            for (int i = 0; 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;
 
 
            b = true;
            s = "123";
            d = 3.13;
        }
 
 
 
    }