Question

As a new .NET 3.5 programmer, I started to learn LINQ and I found something pretty basic that I haven’t noticed before:

The book claims every array implements IEnumerable<T> (obviously, otherwise we couldn’t use LINQ to objects on arrays…). When I saw this, I thought to myself that I never really thought about that, and I asked myself what else all arrays implement – so I examined
System.Array using the object browser (since it’s the base class for every array in the CLR) and, to my surprise, it doesn’t implement IEnumerable<T>.

So my question is: where is the definition? I mean, how can I tell exactly which interfaces every array implements?

Answer 1

From the documentation (emphasis mine):

[…] the Array class implements the System.Collections.Generic.IList<T>, System.Collections.Generic.ICollection<T>, and System.Collections.Generic.IEnumerable<T> generic interfaces. The implementations are provided to arrays at run time, and therefore are not visible to the documentation build tools.

EDIT: as Jb Evain points out in his comment, only vectors (one-dimensional arrays) implement the generic interfaces. As to why multi-dimensional arrays don’t implement the generic interfaces, I’m not quite sure since they do implement the non-generic counterparts (see the class declaration below).

The System.Array class (i.e. every array) also implements these non-generic interfaces:

public abstract class Array : ICloneable, IList, ICollection, IEnumerable, IStructuralComparable, IStructuralEquatable