Testing Equality of Arrays in C#

Question

I have two arrays. For example:

int[] Array1 = new[] {1, 2, 3, 4, 5, 6, 7, 8, 9};
int[] Array2 = new[] {9, 1, 4, 5, 2, 3, 6, 7, 8};

What is the best way to determine if they have the same elements?

Answer 1

I have found the solution detailed here to be a very clean way, though a bit verbose for some people.

The best thing is that it works for other IEnumerables as well.

Answer 2

Will the values always be unique? If so, how about (after checking equal length):

var set = new HashSet<int>(array1);
bool allThere = array2.All(set.Contains);

Answer 3

How about LINQ:

var q = from a in ar1
        join b in ar2 on a equals b
        select a;

bool equals = ar1.Length == ar2.Length && q.Count() == ar1.Length;

Answer 4

var shared = arr1.Intersect(arr2);
bool equals = arr1.Length == arr2.Length && shared.Count() == arr1.Length;

Answer 5

You could also use SequenceEqual, provided the IEnumerable objects are sorted first.

int[] a1 = new[] { 1, 2, 3, 4, 5, 6, 7, 8, 9 };    
int[] a2 = new[] { 9, 1, 4, 5, 2, 3, 6, 7, 8 };    

bool equals = a1.OrderBy(a => a).SequenceEqual(a2.OrderBy(a => a));

Answer 6

Use extension methods (which are new in 3.0). If the length of the Intersection of the two arrays equals that of their Union then the arrays are equal.

bool equals = arrayA.Intersect(arrayB).Count() == arrayA.Union(arrayB).Count()

Succinct.

Answer 7

For the most efficient approach (Reflectored from Microsoft code), see here:

http://stackoverflow.com/questions/50098/comparing-two-collections-for-equality/3790621#3790621