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 … Read more
Basically it was an oversight. In C# 1.0, foreach never called Dispose 1. With C# 1.2 (introduced in VS2003 – there’s no 1.1, bizarrely) foreach began to check in the finally block whether or not the iterator implemented IDisposable – they had to do it that way, because retrospectively making IEnumerator extend IDisposable would have … Read more
IEnumerable is an interface that defines one method GetEnumerator which returns an IEnumerator interface, this in turn allows readonly access to a collection. A collection that implements IEnumerable can be used with a foreach statement. Definition IEnumerable public IEnumerator GetEnumerator(); IEnumerator public object Current; public void Reset(); public bool MoveNext(); example code from codebetter.com
Indeed, it is for performance reasons. The BCL team did a lot of research on this point before deciding to go with what you rightly call out as a suspicious and dangerous practice: the use of a mutable value type. You ask why this doesn’t cause boxing. It’s because the C# compiler does not generate … Read more
for example, when to use it over foreach? You don’t use IEnumerable “over” foreach. Implementing IEnumerable makes using foreach possible. When you write code like: foreach (Foo bar in baz) { … } it’s functionally equivalent to writing: IEnumerator bat = baz.GetEnumerator(); while (bat.MoveNext()) { bar = (Foo)bat.Current … } By “functionally equivalent,” I mean … Read more