var推断类型，foreach循环。

    class Program
    {
        static void Main(string[] args)
        {
            //var:根据值能够推断出来类型
            //c#是一门强类型语言：在代码当中，必须对每一个变量的类型有一个明确的定义
            var n = 15;
            var n2 = "张三";
            var n3 = 3.14;
            var n4 = 5000m;
            var n5 = true;
            var n6 = '男';
            Console.WriteLine(n.GetType());
            Console.WriteLine(n2.GetType());
            Console.WriteLine(n3.GetType());
            Console.WriteLine(n4.GetType());
            Console.WriteLine(n5.GetType());
            Console.WriteLine(n6.GetType());
            Console.ReadKey();

            //var input;
            //input = "张三";


            //js是一门弱类型语言
            //12 3.14 true "fdsfds"  'c'  var
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            //int[] nums = { 1, 2, 3, 4, 5, 6, 76, 7, 8, 23 };
            //for (int i = 0; i < nums.Length; i++)
            //{
            //    Console.WriteLine(nums[i]);
            //}
            //Console.WriteLine("=====================================");
            //foreach (var item in nums)
            //{
            //    Console.WriteLine(item);
            //}
            //Console.ReadKey();
            Stopwatch sw = new Stopwatch();
            int[] nums = new int[1000];
            sw.Start();
            foreach (var item in nums)
            {

            }
            for (int i = 0; i < nums.Length; i++)
            {

            }
            sw.Stop();
            Console.WriteLine(sw.Elapsed);
            Console.ReadKey();
        }
    }