How to compare sets stored in IEnumerable?

Question

For the sake of simplicity I pass along sets as IEnumerable. I need to check, whether two such sets are equal. Currently I'm doing it in the following way:

if (theirs.OrderBy(t => t).SequenceEquals(mine.OrderBy(t => t)))
    // equal

Is there a simpler way?

---

I need this code mainly for series of such comparisons:

if (mine."equals"(new[] { a, b })
{
    do sth
}
else if (mine."equals"(new[] { a, c })
{
    do sth
}
else if (mine.contains(a))
{
    do sth
}
...

Answer 1

If you could actually keep one of them as an ISet<T>, you can just call SetEquals. You could do this optionally, of course:

ISet<Foo> setFoo = theirs as ISet<Foo>;
if (setFoo != null && theirs.SetEquals(mine))
{
    ...
}
// Not a set? Use the slower approach

You don't have to sort the set though - you could do:

if (new HashSet<Foo>(theirs).SetEquals(mine))

for example. As noted in comments, this will treat { 1, 1, 2 } as equal to { 1, 2, 2 } though. Only use set operations if you really have a logical set.