var推断类型，foreach循环。

 1     class Program
 2     {
 3         static void Main(string[] args)
 4         {
 5             //var:根据值能够推断出来类型
 6             //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
 7             var n = 15;
 8             var n2 = "张三";
 9             var n3 = 3.14;
10             var n4 = 5000m;
11             var n5 = true;
12             var n6 = ‘男‘;
13             Console.WriteLine(n.GetType());
14             Console.WriteLine(n2.GetType());
15             Console.WriteLine(n3.GetType());
16             Console.WriteLine(n4.GetType());
17             Console.WriteLine(n5.GetType());
18             Console.WriteLine(n6.GetType());
19             Console.ReadKey();
20 
21             //var input;
22             //input = "张三";
23 
24 
25             //js是一门弱类型语言
26             //12 3.14 true "fdsfds"  ‘c‘  var
27         }
28     }

 1     class Program
 2     {
 3         static void Main(string[] args)
 4         {
 5             //int[] nums = { 1, 2, 3, 4, 5, 6, 76, 7, 8, 23 };
 6             //for (int i = 0; i < nums.Length; i++)
 7             //{
 8             //    Console.WriteLine(nums[i]);
 9             //}
10             //Console.WriteLine("=====================================");
11             //foreach (var item in nums)
12             //{
13             //    Console.WriteLine(item);
14             //}
15             //Console.ReadKey();
16             Stopwatch sw = new Stopwatch();
17             int[] nums = new int[1000];
18             sw.Start();
19             foreach (var item in nums)
20             {
21 
22             }
23             for (int i = 0; i < nums.Length; i++)
24             {
25 
26             }
27             sw.Stop();
28             Console.WriteLine(sw.Elapsed);
29             Console.ReadKey();
30         }
31     }