The generic version of IEnumerable provides a way to make enumeration type-safe. Type mis-matches will show up at compile time rather than run time. Here is a code example.

using System;

using System.Collections;

using System.Collections.Generic;

public class Person
{
  public Person(string fName, string lName)
  {
    this.firstName = fName;
    this.lastName = lname;
  }
  public string firstName;
  public string lastName;
}
//
//Make the class People enumerable on Person
//
public class People : IEnumerable<Person>
{
  private Person[] people;
  public People(Person[] pArray)
  {
    people = new Person[pArray.length];
    for (int i = 0; i < pArray.length; i++)
    {
      people[i] = pArray[i];
    }
  }
  //Implement GetEnumerator for IEnumerable<Person>
  //This implementation works when the variable that holds 
  //the required values is enumerable
  public IEnumerator<Person> GetEnumerator()
  {
    foreach (Person p in people)
    {
      yeild return p;
    }
  }
  //Implement GetEnumerator for the IEnumerable interface that is
  //implied by IEnumerable<Person>.  
  //Use explicit implementation.
  IEnumerator IEnumerable.GetEnumerator()
  {
    foreach (Person p in people)
    {
      yeild return p;
    }
  }
}