C#步骤的练习

using System;using System.Collections.Generic;using System.Linq;using System.Text;namespace Demo1{    class Program    {        /// <summary>        /// 求一个字符串数组中最长的元素        /// </summary>        /// <param name="s"></param>        /// <returns></returns>        public static string GetLongest(string[] s)        {            string max = s[0];            for (int i = 0; i < s.Length; i++)            {                if (s[i].Length > max.Length)                {                    max = s[i];                }            }            return max;        }        static void Main(string[] args)        {            //用方法来实现:有一个字符串数组:            //{"马龙"，"迈克尔乔丹","雷吉米勒","科比"}，请输出最长的那个            string[] names = { "马龙", "迈克尔乔丹", "雷吉米勒", "科比" };            Console.WriteLine(GetLongest(names));        }    }}

using System;using System.Collections.Generic;using System.Linq;using System.Text;namespace Demo1{    class sumnumber    {        /// <summary>        /// 计算出整数数组的平均值并保留2位小数        /// </summary>        /// <param name="nums"></param>        /// <returns></returns>        public double GetAvg(int[] nums)        {            double sum = 0;            for (int i = 0; i < nums.Length;i++ )            {                sum += nums[i];            }            return sum / nums.Length;        }    }}using System;using System.Collections.Generic;using System.Linq;using System.Text;namespace Demo1{    class Program    {            static void Main(string[] args)        {            int[] numbers = { 1, 2, 7 };            sumnumber sber = new sumnumber();            double avg = sber.GetAvg(numbers);            //保留2位小数  将avg转换成string类型            //然后用Convet.ToDouble转换            string str=avg.ToString("0.00");            avg = Convert.ToDouble(str);            Console.WriteLine(avg);            Console.ReadKey();        }    }}