Implementing IEnumerable and IEnumerator on Your Custom Objects

Often you want to be able to enumerate through a collection of objects using the foreach statement in C#:

Using foreach in C#


foreach (Student student in myClass)
        Console.WriteLine(student);

To be able to pull that off, myClass must implement IEnumerable:

IEnumerable Defined

Exposes the enumerator, which supports a simple iteration over a collection.

public IEnumerator GetEnumerator();

As is says above, IEnumerable just exposes another interface, called IEnumerator:

IEnumerator Defined

Supports a simple iteration over a collection. Enumerators only allow reading the data in the collection. Enumerators cannot be used to modify the underlying collection.

public object Current;
public void Reset();
public bool MoveNext();

To see this in action, let's create an example by which we can iterate through a list of students in a class using the foreach statement in C#.

First, we need to create a Student Class as shown below. At the minimum we want to override ToString() (Overriding System.Object.ToString() and IFormattable) so it says something meaningful and for kicks I decided to override Equals() and GetHashCode() (Object Identity vs. Object Equality - Overriding System.Object.Equals(Object obj)) only as an example.

Implementing IEnumerable and IEnumerator on Your Custom Objects

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