IEnumerable & amp; IEnumerator, c # ienumerable

IEnumerable & IEnumerator, c # ienumerable
IEnumerable has only one method: IEnumerator GetEnumerator (). INumerable is an interface that the set should implement. In this way, you can use foreach to traverse the set. IEnumerator has the Current attribute, MoveNext (), and Reset () methods. When foreach uses an IEnumerable set, traversal starts like this: 1. Call GetEnumerator () to get an IEnumerator object. 2. Call MoveNext (); 3. Use one of the objects. 4. repeat 2 and 3 until MoveNext () returns false (no more ). 1. at the beginning of the object returned by GetEnumerator (), the pointer is placed before the first object, and the same is true after Reset. 2. To use foreach, implementing IEnumerable is not a must, but a best practice. Here is an example provided by Microsoft:

using System;using System.Collections;// Simple business object.public class Person{    public Person(string fName, string lName)    {        this.firstName = fName;        this.lastName = lName;    }    public string firstName;    public string lastName;}// Collection of Person objects. This class// implements IEnumerable so that it can be used// with ForEach syntax.public class People : IEnumerable{    private Person[] _people;    public People(Person[] pArray)    {        _people = new Person[pArray.Length];        for (int i = 0; i < pArray.Length; i++)        {            _people[i] = pArray[i];        }    }// Implementation for the GetEnumerator method.    IEnumerator IEnumerable.GetEnumerator()    {       return (IEnumerator) GetEnumerator();    }    public PeopleEnum GetEnumerator()    {        return new PeopleEnum(_people);    }}// When you implement IEnumerable, you must also implement IEnumerator.public class PeopleEnum : IEnumerator{    public Person[] _people;    // Enumerators are positioned before the first element    // until the first MoveNext() call.    int position = -1;    public PeopleEnum(Person[] list)    {        _people = list;    }    public bool MoveNext()    {        position++;        return (position < _people.Length);    }    public void Reset()    {        position = -1;    }    object IEnumerator.Current    {        get        {            return Current;        }    }    public Person Current    {        get        {            try            {                return _people[position];            }            catch (IndexOutOfRangeException)            {                throw new InvalidOperationException();            }        }    }}class App{    static void Main()    {        Person[] peopleArray = new Person[3]        {            new Person("John", "Smith"),            new Person("Jim", "Johnson"),            new Person("Sue", "Rabon"),        };        People peopleList = new People(peopleArray);        foreach (Person p in peopleList)            Console.WriteLine(p.firstName + " " + p.lastName);    }}/* This code produces output similar to the following: * * John Smith * Jim Johnson * Sue Rabon * */