C# IEnumerable Interface - ienumerable

Question

I am trying to understand this example from a MSDN article, to my understanding with the IEnumberable interface, we will be able to use Foreach to loop through the class collection, I am confused at the Main method, why don't we just use:
foreach (Person p in peopleArray)
Console.WriteLine(p.firstName + " " + p.lastName);
instead of
People peopleList = new People(peopleArray);
foreach (Person p in peopleList)
Console.WriteLine(p.firstName + " " + p.lastName);
Example:
using System;
using System.Collections;
public class Person
{
public Person(string fName, string lName)
{
this.firstName = fName;
this.lastName = lName;
}
public string firstName;
public string lastName;
}
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];
}
}
IEnumerator IEnumerable.GetEnumerator()
{
return (IEnumerator) GetEnumerator();
}
public PeopleEnum GetEnumerator()
{
return new PeopleEnum(_people);
}
}
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);
}
}

Answer 1

You're right, you could simply use the first version because arrays implement IEnumerable.
The reason they chose to iterate over People is simply for academic purposes; to demonstrate how iterators work (and how to implement IEnumerable). If they simply iterated over peoplearray, they wouldn't be using the People class, which is the main focus of that example.