Iterator In C# 2.0

Introduction

You can iterate over data structures such as arrays and collections using a foreach loop.

string[] cities = { "New York", "Paris", "London" };
foreach (string city in cities)
{
    // Your code for each city goes here
    Console.WriteLine(city);
}

In fact, you can use any custom data collection in the foreach loop, as long as that collection type implements a GetEnumerator method that returns an IEnumerator interface. Usually you do this by implementing the IEnumerable interface.

public interface IEnumerable
{
    IEnumerator GetEnumerator();
}
public interface IEnumerator
{
    object Current { get; }
    bool MoveNext();
    void Reset();
}

Iterator is one of the new feature in c# 2.0 which provide a way to create classes that can be used with foreach statement without implementing the IEnumerator & IEnumerable interfaces when compiler detects iterator it will automatically generate the current, MoveNext and dispose method of IEnumerable or IEnumerator interface. Here I explain with employees and department classes GetEnumerator method, typically by implementing IEnumerable or IEnumerable <ItemType>. You tell the compiler what to yield using the new C# yield return statement.

Employees

using System;
using System.Collections.Generic;
using System.Text;
namespace CsharpIterators
{
    class Department
    {
        private List<Employees> _employees;
        private string _name;
        public string DepartmentName
        {
            get { return _name; }
            set { _name = value; }
        }
        public Department(string name)
            : this()
        {
            _name = name;
        }
        public Department()
        {
            _employees = new List<Employees>(5);
        }
        public void AddEmployees(Employees emp)
        {
            _employees.Add(emp);
        }
        public IEnumerator<Employees> GetEnumerator()
        {
            foreach (Employees emp in _employees)
                yield return emp;
        }
    }
}

Program

using System;
using System.Collections.Generic;
using System.Text;
namespace CsharpIterators
{
    class Program
    {
        static void Main(string[] args)
        {
            Employees emp1 = new Employees("Jack");
            Employees emp2 = new Employees("Radu");
            Employees emp3 = new Employees("Emali");
            Employees emp4 = new Employees("Jecci");
            Department dept = new Department("MyDepartment");
            dept.AddEmployees(emp1);
            dept.AddEmployees(emp2);
            dept.AddEmployees(emp3);
            dept.AddEmployees(emp4);
            foreach (Employees emp in dept)
            {
                Console.WriteLine(emp.EmployeeName);
            }
        }
    }
}