a sample of Interators

using System;
using System.Collections;

class List
...{
    string []list=new string[5]...{"Mon","Tue","Wed","Thu","Fri"};
    
    public IEnumerator GetEnumerator()
    ...{
        for(int i=0;i<5;i++)
        ...{
            yield return list[i];
        }
    }
}

class Client
...{
    static void Main()
    ...{
        List list=new List();
        
        foreach(string day in list)
        ...{
            Console.Write(day+" ");
        }
    }
}

 

foreach默认调用list.GetEnumerator(). 

 

...{
    IEnumerator enumerator MessageSet.GetEnumerator();
    string nextMessage;
    enumerator.MoveNext;
    while((nextMessage=enumerator.Current)!=null)
    ...{
        DoSomething(nextMessage);
        enumerator.MOveNext();
    }
}

 

understand "yield" key word.

class Client
...{
    static void Main()
    ...{
        /**//*List list=new List();
        
        foreach(string day in list)
        {
            Console.Write(day+" ");
        }*/
         
        a aa=new a();
         

        foreach(string str in aa)
        ...{
            Console.Write(str+" ");
        }
    }
}

class a
...{
    public IEnumerator GetEnumerator()
    ...{
        yield return "Just";
        yield return "for";
        yield return "you";
        yield return "!";
    }
}