Design Pattern iterator mode

Speaking of iterators, we must not be strangers, often using the foreach in this loop is that the C # language has built-in iterator pattern, mainly support for non-generic collection of simple iterative interface Ieumerator and public enumerator IEnumerable. Although built-in, this model also has the need for us to learn.

The code is as follows

usingSystem;usingSystem.Collections.Generic;usingSystem.Linq;usingSystem.Text;usingSystem.Threading.Tasks;namespacedesign Pattern iterator pattern { Public Abstract classIterator//Abstract iterators    {         Public Abstract ObjectFirst ();  Public Abstract ObjectNext ();  Public Abstract ObjectCurrent ();  Public Abstract BOOLIsmax (); }     Public Abstract classAggregate//abstract objects that are iterated    {         Public AbstractIterator createiterator (); }     Public classAiterator:iterator//Specific iterators    {         PublicAaggregate ListA =NewAaggregate ();//storing objects that are iterated        Private intCurrent=0;  PublicAiterator (Aaggregate a)//an object that is bound to be iterated when initialized{ListA=A; }         Public Override ObjectFirst ()//get the object for the first iteration        {            returnlista[0]; }         Public Override ObjectNext ()//gets the next object of the current object{ Current++; if(Current <Lista.count ()) {                returnLista[current]; }            Else            {                return NULL; }        }         Public Override ObjectCurrent ()//get Current Object        {            returnLista[current]; }         Public Override BOOLIsmax () {returnCurrent = = Lista.count ()?true:false; }    }     Public classAaggregate:aggregate//the specific iterated object, the iterative direction is forward.     {         Publicilist<Object> lists =Newlist<Object>();  Public OverrideIterator Createiterator ()//an iterative device for creating iterative objects        {            return NewAiterator ( This); }         Public intCount ()//get the number of iterated objects        {            returnlists.        Count; }         Public Object  This[intIndex//Indexer        {            Get            {                returnLists[index]; }            Set{lists.            Insert (index, value); }        }    }     Public classBiterator:iterator { PublicAaggregate blist =Newaaggregate (); Private intCurrent=0;  PublicBiterator (Aaggregate a) {blist=A; Current= A.count ()-1; }         Public Override ObjectCurrent () {returnBlist[current]; }         Public Override ObjectFirst () {returnBlist[blist. Count ()-1]; }         Public Override BOOLIsmax () {returncurrent<0?true:false; }         Public Override ObjectNext () { current--; if(current>=0)            {                returnBlist[current]; }            return NULL; }    }    classProgram {Static voidMain (string[] args) {Aaggregate a=Newaaggregate (); a[0] ="Hello"; a[1] ="Are you really okay? "; a[2] ="you're a bloody sick man! Lao Tzu is good."; Aiterator b=NewAiterator (a);  while(!B.ismax ())                {Console.WriteLine (B.current ());            B.next ();            } Console.WriteLine (); Biterator C=NewBiterator (a);  while(!C.ismax ())                {Console.WriteLine (C.current ());            C.next ();        } console.read (); }    }}

Operation Result:

Design Pattern iterator mode