Linq - what locale/collation it uses to compare objects?

Question

When I call a Linq (not Linq-for-SQL, just simple in-memory Linq) - what locale it uses to compare objects, and how can I affect it?

E.g.

string[] a = { "a", "b", ... };
string max = a.Max();

What locale is used here - current, invariant? How can I affect it? The comparision seems to be case-insensitive, what if I want to find case-sensitive max?

Answer 1

It uses the implementation of IComparable<string> in string.

You could fairly easily write your own version of Max which does take an IComparer<T> for comparisons - I'm very surprised there isn't one already. Alternatively, you could use Aggregate in a somewhat cumbersome way to accomplish the same result.

Answer 2

I decided to take a deeper look on what happening.

Max method uses Comparer class to compare items. Comparer class in turn uses GenericComparer.Compare method. This method calls String.CompareTo method. CompareTo uses following code:

CultureInfo.CurrentCulture.CompareInfo.Compare(this, strB, CompareOptions.None);

That said, you can affect behavior of Max method by changing

Thread.CurrentThread.CurrentCulture

If it's unacceptable, you have to roll out your own version of Max as Jon suggested.

Answer 3

Posting my code based on Jon's suggestion:

static T Max<T>(this IEnumerable<T> coll, IComparer<T> comp)
{
    return coll.Aggregate((a, b) => comp.Compare(a, b) < 0 ? b : a);
}

It can be used as

string max = coll.Max(StringComparer.OrdinalIgnoreCase);