C#: Compare contents of two IEnumerables

There are quite a few ways. Assume A and B is IEnumerable.

!A.Except(B).Any() && !B.Except(A).Any()
A.Count() == B.Count() && A.Intersect(B).Count() == B.Count()
etc

Try the HashSet class:

var enumA = new[] { 1, 2, 3, 4 };
var enumB = new[] { 4, 3, 1, 2 };

var hashSet = new HashSet<int>(enumA);
hashSet.SymmetricExceptWith(enumB);
Console.WriteLine(hashSet.Count == 0); //true => equal

But that does only work correctly if the values are distinct.

For example

var enumA = new[] { 1, 1, 1, 2 };
var enumB = new[] { 1, 2, 2, 2 };

are also considered as "equal" with the mentioned method.

Sticking with your example, you can make both of IEnumerable to be of type List and then use SequenceEqual as the example below:

var first = Enumerable.Range(1, 3);
var second = Enumerable.Range(1, 3);
var areTheyEqual = first.ToList().SequenceEqual(second.ToList());
if (areTheyEqual)
{ /* do something... */}

I did this for merging new items into a collection without duplicates, it takes two collections and returns all the items with out any duplicates

List<Campaign> nonMatching = (from n in newCampaigns 
where !(from e in Existing select e.Id).Contains<int>(n.Id) 
select n).ToList<Campaign>();

Now by removing the ! for the contains statement

List<Campaign> nonMatching = (from n in newCampaigns 
where (from e in Existing select e.Id).Contains<int>(n.Id) 
select n).ToList<Campaign>();

it will return the duplicates

To compare the data in the two objects, I simply used this

A.Except(B).Any() || B.Except(A).Any()

I think ordering the sequence is the fastest way you can achieve this.

If you're really just testing to see if there are duplicates, then leppie's suggestion should work:

if (A.Except(B).Count == 0 && B.Except(A).Count == 0) {...}

But if you just need to arrive at an IEnumerable with no duplicates:

var result = A.Union(B).Distinct();