Difference between IEnumerable and IEnumerator

 

IEnumerable:

•  It contains only one method and the return type is IEnumerator
• The Method name is GetEnumerator
• Below is the Default Syntax
• IEnumerable doesn't maintain States (currently, it does not know which row is iterating )
• It is an Interface
• the list class resides in "using System.Collections.Generic"
• Syntax is shart 
• Actually, IEnumerable uses the IEnumerator internally.

namespace System.Collections.Generic {     public interface IEnumerable<out T> : IEnumerable     {       merator<T> GetEnumerator();     } }

IEnumerator:

• It contains 2 methods and one property
• IEmerator is an Interface
• It Maintains States (currently, it knows which row is iterating )
• it maintains the current property and MoveNext and Reset Method
•  the list class resides in "using System.Collections.Generic"
• The syntax is not shart 

using System.Runtime.InteropServices;  namespace System.Collections {        public interface IEnumerator     {          object Current { get; }          bool MoveNext();           void Reset();     } }

States:

• The Biggest Different between them is States, now I am showing below snippet
• IEnumerable doesn't maintain states
• IEnumerator maintain states

using System; using System.Collections.Generic; namespace ConsolePractice {     class Program     {         static void Main(string[] args)         {             List<int> list = new List<int>();             list.Add(995);             list.Add(996);             list.Add(997);             list.Add(998);             list.Add(999);             list.Add(2000);             list.Add(2001);             list.Add(2002);             list.Add(2003);             list.Add(2004);             list.Add(2005);              IEnumerator<int> ienumerator =list.GetEnumerator();             statemaintsin95to2000(ienumerator);              Console.ReadLine();         }         static void statemaintsin95to2000(IEnumerator<int> ienumerator)         {          Console.WriteLine("Before Iterating the IEnumerator from 95 to 2000");             while (ienumerator.MoveNext())             {                if (Convert.ToInt32(ienumerator.Current) >= 2000)                 {                     statemaintsin2000to2005(ienumerator);                 }                 Console.WriteLine(ienumerator.Current.ToString());             }         }         static void statemaintsin2000to2005(IEnumerator<int> ienumerator)         {         Console.WriteLine("After Iterating the IEnumerator from 95 to 2000");             while (ienumerator.MoveNext())             {                 Console.WriteLine(ienumerator.Current.ToString());             }         }     } }

Simple Iteration using List, IEnumerable and IEnumerator

using System; using System.Collections.Generic; namespace ConsolePractice {     class Program     {         static void Main(string[] args)         {             List<int> list = new List<int>();             list.Add(995);             list.Add(996);             list.Add(997);             list.Add(998);             list.Add(999);             list.Add(2000);             list.Add(2001);             list.Add(2002);             list.Add(2003);             //iterate by using the list             Console.WriteLine("Iterating List");             foreach (int i in list)             {                 Console.WriteLine(i);             }             //iterating the IEnumeraable             Console.WriteLine("Iterating the IEnumerable");             IEnumerable<int> ienumerable = (IEnumerable<int>)list;             foreach (int i in ienumerable)             {                 Console.WriteLine(i);              }             //iterating the ienumerator             Console.WriteLine("Iterating the IEnumerator");             IEnumerator<int> ienumerator = list.GetEnumerator();              while (ienumerator.MoveNext())             {               Console.WriteLine(ienumerator.Current.ToString());             }              Console.ReadLine();         }     } }