Question

i am quite confused about the differences between the various types in the C# language. specifically

• IEnumerable
• IEnumerator

Answer 1

IEnumerable<T> represents a sequence which can be enumerated – such as a list.

IEnuerator<T> effectively represents a cursor within a sequence.

So imagine you have a sequence – you can iterate over that with several “cursors” at the same time. For example:

List<string> names = new List<string> { "First", "Second", "Third" };
foreach (string x in names)
{
    foreach(string y in names)
    {
        Console.WriteLine("{0} {1}");
    }
}

Here, List<string> implements IEnumerable<string>, and the foreach loops each call GetEnumerator() to retrieve an IEnumerator<string>. So when we’re in the middle of the inner loop, there are two independent cursors iterating over a single sequence.