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I was implementing my own ArrayList class and was left surprised when I realised that
public System.Collections.Generic.IEnumerator<T> GetEnumerator() { return _array.GetEnumerator(); } didn't work. What is the reason arrays don't implement IEnumerator in .NET?
Is there any work-around?
Thanks
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All arrays implement IList, and IEnumerable. You can use the foreach statement to iterate through an array.
IEnumerable is an interface defining a single method GetEnumerator() that returns an IEnumerator interface. It is the base interface for all non-generic collections that can be enumerated. This works for read-only access to a collection that implements that IEnumerable can be used with a foreach statement.
IEnumerable<T> is the base interface for collections in the System. Collections. Generic namespace such as List<T>, Dictionary<TKey,TValue>, and Stack<T> and other generic collections such as ObservableCollection<T> and ConcurrentStack<T>.
IEnumerable is conceptually faster than List because of the deferred execution. Deferred execution makes IEnumerable faster because it only gets the data when needed. Contrary to Lists having the data in-memory all the time.
Arrays do implement IEnumerable<T>, but it is done as part of the special knowledge the CLI has for arrays. This works as if it were an explicit implementation (but isn't: it is done at runtime). Many tools will not show this implementation, this is described in the Remarks section of the Array class overview.
You could add a cast:
return ((IEnumerable<T>)_array).GetEnumerator(); Note, older MSDN (pre docs.microsoft.com) coverage of this changed a few times with different .NET versions, check for the remarks section.
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