does array implements IEnumerable?

Question

I know that the base abstract Array class doesn't implement generic IEnumerable as

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

so when I create a derive array class like int[] i; or string[] s;, do they implement IEnumerable<T>? And how can I see the source code of []?

https://stackoverflow.com/questions/11163297/how-do-arrays-in-c-sharp-partially-implement-ilistt — Hans Passant, Jun 06 '19 at 06:39
https://mattwarren.org/2017/05/08/Arrays-and-the-CLR-a-Very-Special-Relationship/ may be worth a read. — mjwills, Jun 06 '19 at 07:00
Matt Warren does point to that stackoverflow link for further reading @HansPassant. — mjwills, Jun 06 '19 at 23:10

score 3 · Answer 1 · answered Jun 06 '19 at 06:34

3

Official word here

Array Overview

An array has the following properties:

An array can be Single-Dimensional, Multidimensional or Jagged.

The number of dimensions and the length of each dimension are established when the array instance is created. These values can't be changed during the lifetime of the instance.

The default values of numeric array elements are set to zero, and reference elements are set to null.

A jagged array is an array of arrays, and therefore its elements are reference types and are initialized to null.

Arrays are zero indexed: an array with n elements is indexed from 0 to n-1.

Array elements can be of any type, including an array type.

Array types are reference types derived from the abstract base type Array. Since this type implements IEnumerable and IEnumerable<T>, you can use foreach iteration on all arrays in C#.

answered Jun 06 '19 at 06:34

TheGeneral

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This is a mighty fine summary of `Array`, but it doesn't answer the question "And how can I see the source code of `[]`?" – Enigmativity Jun 06 '19 at 06:50
@TheGeneral is it the reason we can use extension methods in `System.Linq.Enumerable` because the derived array types do implement IEnumerable despite the fact that base Array class doesn't? – Jun 06 '19 at 06:51
@Enigmativity and there be the fly in the anointment (again). technically there isn't really its compiled – TheGeneral Jun 06 '19 at 06:52

score 3 · Answer 2 · answered Jun 06 '19 at 06:38

3

There is special type SZArrayHelper - wrapper around array. Here is source code: https://referencesource.microsoft.com/#mscorlib/system/array.cs,aa97964558672440

Also, array implements IList, and it implements ICollection and it implements IEnumerable. So, Array implements IEnumerable

answered Jun 06 '19 at 06:38

Backs

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You got to love the constructor `Contract.Assert(false, "Hey! How'd I get here?");` someone at Microsoft has a sense of humour, also plus 1 – TheGeneral Jun 06 '19 at 06:46
@TheGeneral i've found it after investigating another problem: http://blog.rogatnev.net/2017/07/14/IndexOf-with-IEquatable.html – Backs Jun 06 '19 at 07:56

score 2 · Answer 3 · answered Jun 06 '19 at 08:31

You can check it simply like this:

var type = typeof(int[]); // or any other type
foreach (var @interface in type.GetInterfaces())
    Console.WriteLine(@interface);

Result is:

System.ICloneable
System.Collections.IList
System.Collections.ICollection
System.Collections.IEnumerable
System.Collections.IStructuralComparable
System.Collections.IStructuralEquatable
System.Collections.Generic.IList`1[System.Int32]
System.Collections.Generic.ICollection`1[System.Int32]
System.Collections.Generic.IEnumerable`1[System.Int32]
System.Collections.Generic.IReadOnlyList`1[System.Int32]
System.Collections.Generic.IReadOnlyCollection`1[System.Int32]

does array implements IEnumerable?

3 Answers3