What is the difference between IEnumerable and Foreach loop

Question

Can anyone explain me the difference between the both when should I use IEnumerable and Foreach loop as both are used for looping the collections.

Nitin Sontakke · Answer

Hello I am not the expert on the subject however to the best of my knowledge when you start iterating your pointer is NOT at the first element but before that. Which you can say is a ghost position. You cannot access any data at that time. This is similar to SqlDataRead.Read() where the first call reads the first record if found otherwise returns false. So in this case first .MoveNext() reads the first element second second and third third. After that it returns false and loop terminates. The execution of first .MoveNext method makes the first element Current. To gain excellent understanding of this (and many other) concepts please do see Jamie King's C# videos on YouTube. Really very good and helpful.

Khaja Moizuddin · Answer

Gnanavel I have a little confusion in Movenext method see the below code using System.Collections.Generic; class Program { static void Main() { List list = new List (); list.Add(1); list.Add(5); list.Add(9); List .Enumerator e = list.GetEnumerator(); Write(e); } static void Write(IEnumerator e) { while (e.MoveNext()) { int value = e.Current; Console.WriteLine(value); } } } We are getting output as 159 If in a list we have 3 elements say 159. When performing e.MoveNext() it will check the next element in the collectionon first element it will check 2ND element ie.5 on 2ND element it will check next element ie.9 on 3rd element it will check next element in the collection hence condition fails then how we are getting output as 159 Can anyone explain me this.

Saravanan Ponnusamy · Answer

Simple IEnumerable is a Collection of data foreach is a iteration of data's or iteration of collection's eg: foreach (string File in Directory.EnumerateFiles(FilePath *.csv))//enum is a collection and foreach for iteration { }

Gnanavel Sekar · Answer

Hi Khaja The cost of allocating the enumerator object by entityList.GetEnumerator(). The cost of two virtual methods calls (MoveNext and Current) for each element of the list. IEnumerable.GetEnumerator() returns an enumerator object (which implements IEnumerator). This has a property Current which returns the current item and a method MoveNext() which advances the enumerator on to the next item. This is all the foreach loop needs to perform the foreach. It simply assigns the Current property to a variable then executes .MoveNext() each time. Usually when you implement IEnumerable on a class you know where the source is coming from. So if you had a class such as this public class MyEnumerable { private List items; } The implementation of IEnumerable would look like this public class MyEnumerable : IEnumerable { private List items; public IEnumerator GetEnumerator() { return items.GetEnumerator(); } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return items.GetEnumerator(); } } Notice that the enumerator is coming from the list object so you don't have to worry about creating an enumerator (though you can if you need to by implementing IEnumerator) For More https://stackoverflow.com/questions/21470793/what-is-the-link-between-foreach-and-ienumerable

Sundar · Answer

IEnumerable is used to hold the Data (Collect Data) Foreach is used to Iterate the Collected Data.

Gokhul Varman · Answer

Refer the link for more detailed explantion you can get a clear solution:https://stackoverflow.com/questions/44220/difference-between-foreach-and-for-loops-over-an-ienumerable-class-in-c-sharp

Amit Gupta · Answer

Long and detailed answer can be found on the below link http://www.c-sharpcorner.com/UploadFile/0c1bb2/ienumerable-interface-in-C-Sharp/ https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/foreach-in Hope you understand the difference

Khaja Moizuddin · Answer

Hello Amit gupta  i am not clear with your answer can you explain me with your small example  in which situation i need to use IEnumerator / IEnumerable compared to Foreach loop ?

Amit Gupta · Answer

Short answer IEnumerable is a collection of data Whereas foreach loop is used to iterate the collection in a foreward only process.