From the documentation (emphasis mine):
[…] the Array class implements the
System.Collections.Generic.IList<T>
,System.Collections.Generic.ICollection<T>
, andSystem.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