c#-foreach的秘密

 

foreach的秘密

class Program

    {

        static void Main(string[] args)

        {

            //创建Person的对象

            Person p1=new Person();

 

            //遍历p1因为实现了IEnumerable接口

            foreach (var item in p1)

            {

                Console.WriteLine(item);

            }

            

            Console.ReadKey();

        }

    }

 

    //实现了Ienumerable接口就可以遍历对象了

    //实现IIndextor因为EnumeratorIndex是泛型类需要实现IIndextor接口

    public class Person:IEnumerable,IIndextor

    {

        public string[] strs = new string[6];

        

        public string this[int Index]

        {

            get { return strs[Index]; }

            set { strs[Index] = value; }

        }

 

        public Person()

        {

            strs[0] = "3sfgew";

            strs[1] = "322";

            strs[2] = "34";

            strs[3] = "3434";

            strs[4] = "3ww";

            strs[5] = "3sdfe";

        }

 

        public IEnumerator GetEnumerator()

        {

            //返回Ienumerator的实现类

            return new EnumeratorIndex<Person>(this);

        }

 

        public int IndexLength

        {

            get { return strs.Length; }

        }

    }

 

    //定义索引器的接口

    public interface IIndextor

    {

        string this[int Index] { get; }

        int IndexLength { get; }

    }

 

    public class EnumeratorIndex<T> : IEnumerator where T:IIndextor

    {

        T p1;

 

        int Index;

 

        //构造函数

        public EnumeratorIndex(T p1)

        {

            //给必须的对象赋值

            //Index的初始值必须是-1

            Index = -1;

            this.p1 = p1;

        }

 

        //返回当前的对象

        public object Current

        {

            get { return p1[Index]; }

        }

 

        //使索引前进到下一个

        public bool MoveNext()

        {

            if (Index < p1.IndexLength - 1)

            {

                Index++;

                return true;

            }

            else

            {

                return false;

            }

        }

 

        //初始化索引

        public void Reset()

        {

            Index = -1;

        }

    }