数组操作帮帮忙求求了

解决了你的问题能点击右上角的采纳吗，谢谢~~

1，

using System;
using System.Linq;
namespace ConsoleApp1
{
  
    class Program
    {
        static void Main(string[] args)
        {
            var rnd = new Random();
            int []arr = new int[100];
            for (var i = 0; i < 100; i++) arr[i] = rnd.Next(1001);
            var rs = arr.Where(i => i % 7 == 0 && i % 3 == 2);
            if (rs.Count() == 0) Console.WriteLine("不存在符合条件的数组项！");
            else Console.WriteLine("符合条件的数字有："+String.Join(",", rs));
            Console.ReadKey();
        }
    }
}

2.

using System;
using System.Linq;
namespace ConsoleApp1
{
  
    class Program
    {
        static void Main(string[] args)
        {
            var rnd = new Random();
            int []arr = new int[100];
            for (var i = 0; i < 100; i++) arr[i] = rnd.Next(301);
            var r = arr.Where(i => i % 2 == 0).Sum();
            Console.Write("偶数和为：" + r);
            Console.ReadKey();
        }
    }
}

3

using System;
using System.Linq;
namespace ConsoleApp1
{
  
    class Program
    {
        static void Main(string[] args)
        {
            string s = "abcDefGHIj";
            int upperCase = 0, lowerCase = 0;
            foreach (var c in s)
            {
                if (c >= 'a' && c <= 'z') lowerCase++;
                if (c >= 'A' && c <= 'Z') upperCase++;
            }

            Console.Write("大写个数：{0}\n小写个数：{1}", upperCase, lowerCase);
            Console.ReadKey();
        }
    }
}

C还是C#?