C#基础（8）——高级参数out、ref、params

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1、out

一个方法返回不同类型的值，如int、string、char等，需要out。

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace ChuangzhiConsel{    class Program    {        static void Main(string[] args)        {            int[] n = new int[11];            int re_max;            int re_min;            double re_sum;            double re_avg;            Random r = new Random();            for (int i = 0; i < n.Length; i++)            {                n[i] = r.Next(0, 12);                Console.Write("{0}  ", n[i]);            }            Test(n, out re_max, out re_min, out re_sum, out re_avg);            //真正将re_avg保留两位            Console.WriteLine("\n返回的最大值：{0}，最小值：{1}，总和：{2}，均值：{3:0.000}", re_max, re_min, re_sum, re_avg);            re_avg = Convert.ToDouble(re_avg.ToString("0.00"));            Console.WriteLine("真正re_avg保留两位：{0}", re_avg);            Console.ReadKey();        }        /// <summary>        /// 计算最大、最小、总和、均值        /// </summary>        /// <param name="nums"></param>        /// <param name="max"></param>        /// <param name="min"></param>        /// <param name="sum"></param>        /// <param name="avg"></param>        public static void Test(int[] nums, out int max, out int min, out double sum, out double avg)        {            max = int.MinValue;            min = int.MaxValue;            sum = 0;            avg = 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;            }        }    }}

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使用多余out，进行用户的登录

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace ChuangzhiConsel{    class Program    {        static void Main(string[] args)        {            string msg;//不需要赋值，因为函数有返回值            bool islogin = false;            do            {                Console.WriteLine("用户名：");                string name = Console.ReadLine();                Console.WriteLine("密码：");                string passwd = Console.ReadLine();                islogin = Is_Login(name, passwd, out msg);                Console.WriteLine(msg);            } while (!islogin);            Console.ReadKey();        }        public static bool Is_Login(string logname, string pwd, out string msg)        {            if (logname == "admin" && pwd == "123")            {                msg = "登录成功，欢迎回来！";                return true;            }            else if (logname != "admin")//只能选中其中一种情况            {                msg = "登录名错误！";                return false;            }            else if (pwd != "123")            {                msg = "密码错误！";                return false;            }            else            {                msg = "未知错误...";                return false;            }        }    }}

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out参数

int.TryParse的模仿：
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2、ref

将实参代入方法中进行修改，返回修改后了的值，不需要return一个定义的形参；

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace ChuangzhiConsel{    class Program    {        static void Main(string[] args)        {            double salary;            Console.WriteLine("请输入当前薪水：");            salary  = Convert.ToDouble(Console.ReadLine());            TestRef(ref salary);//没有声明类型接收            Console.WriteLine("加薪后：{0}", salary);            Console.ReadKey();        }        public static void TestRef(ref double s)//没有返回类型        {            s += 500;        }    }}

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交换两个数字

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace ChuangzhiConsel{    class Program    {        static void Main(string[] args)        {            int num1 = 10;            int num2 = 20;            TestRef(ref num1, ref num2);            Console.WriteLine("交换后：num1={0}  num2={1}",num1,num2);            Console.ReadKey();        }        /// <summary>        /// 用于不另外开辟变量的情况下，交换两个变量值        /// </summary>        /// <param name="n1">第一个变量</param>        /// <param name="n2">第二个变量</param>        public static void TestRef(ref int n1,ref int n2)//没有返回类型        {            n1 = n1 - n2;            n2 = n1 + n2;            n1 = n2 - n1;        }    }}

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判断两个数字的大小：

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace ChuangzhiConsel{    class Program    {        public static int i = 0;        static void Main(string[] args)        {            Console.WriteLine("第一个数字：");            int n1 = GetInt(Console.ReadLine());             Console.WriteLine("第二个数字：");            int n2 = GetInt(Console.ReadLine());            JudgeNumber(ref n1, ref n2);            Console.WriteLine("最后的两个数：{0},{1}", n1, n2);            Console.ReadKey();        }        public static int GetInt(string s)        {            while (true)            {                try                {                    int number = Convert.ToInt32(s);                    return number;                }                catch                {                    Console.WriteLine("输入有误！请重新输入：");                    s = Console.ReadLine();                }            }        }        public static void JudgeNumber(ref int n1, ref int n2)        {            while (true)            {                if (n1 < n2)                {                    return;                }                else                {                    Console.WriteLine("再次第一个数字：");                    n1 = GetInt(Console.ReadLine());                    Console.WriteLine("再次第二个数字：");                    n2 = GetInt(Console.ReadLine());                }            }        }    }}

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params

params可变参数，且参数为最后的定义，用于减少声明的参数，如改进前：

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace ChuangzhiConsel{    class Program    {        static void Main(string[] args)        {            int[] array = { 1, 2, 3, 4, 5 };            Tets("张三", array);            Console.ReadKey();        }        public static void Tets(string name, int[] grade)        {            int sum = 0;            for (int i = 0; i < grade.Length; i++)            {                sum += grade[i];            }            Console.WriteLine("{0}的总成绩是：{1}", name, sum);        }    }}

改进后：

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace ChuangzhiConsel{    class Program    {        static void Main(string[] args)        {            //int[] array = { 1, 2, 3, 4, 5 };            Tets("张三", 1, 2, 3, 4, 5);            Console.ReadKey();        }        public static void Tets(string name, params int[] grade)        {            int sum = 0;            for (int i = 0; i < grade.Length; i++)            {                sum += grade[i];            }            Console.WriteLine("{0}的总成绩是：{1}", name, sum);        }    }}

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