Foreach 原理

 1  public class Person
 2     {
 3         private string[] friends = { "asf", "ewrqwe", "ddd", "eeee" };
 4         public string name { get; set; }
 5 
 6         public int age { get; set; }
 7         //这是第一种方法 
 8         public IEnumerable ForEach()
 9         {
10             for (int i = 0; i < friends.Length; i++)
11             {
12                 yield return friends[i];
13             }
14         }
15 }

调用

 1  class Program
 2     {
 3         static void Main(string[] args)
 4         {
 5             Person p = new Person();
 6            
 7             foreach (var item in p.ForEach())
 8             {
 9                 Console.WriteLine(item);
10             }
11          
12             Console.Read();
13         }
14     }

第二种 方法

 

  class Program
    {
        static void Main(string[] args)
        {
            Person p = new Person();
           
            foreach (var item in p)
            {
                Console.WriteLine(item);
            }
         
            Console.Read();
        }
    }

    public class Person
    {
        private string[] friends = { "asf", "ewrqwe", "ddd", "eeee" };
        public string name { get; set; }

        public int age { get; set; }

        //这是第二种
        ////当返回值类型是IEnumerator时，
        //编译器帮我们生成了一个“枚举器”类，
        //即：一个实现了IEnumerator接口的类型。
        public IEnumerator GetEnumerator()
        {
            for (int i = 0; i < friends.Length; i++)
            {
                yield return friends[i];
            }
        }
    }

View Code