Does Any() stop on success?

Question

To be more specific: will the Linq extension method Any(IEnumerable collection, Func predicate) stop checking all the remaining elements of the collections once the predicate has yielded true for an item?

Because I don't want to spend to much time on figuring out if I need to do the really expensive parts at all:

if(lotsOfItems.Any(x => x.ID == target.ID))
    //do expensive calculation here

So if Any is always checking all the items in the source this might end up being a waste of time instead of just going with:

var candidate = lotsOfItems.FirstOrDefault(x => x.ID == target.ID)
if(candicate != null)
     //do expensive calculation here

because I'm pretty sure that FirstOrDefault does return once it got a result and only keeps going through the whole Enumerable if it does not find a suitable entry in the collection.

Does anyonehave information about the internal workings of Any, or could anyone suggest a solution for this kind of decision?

Also, a colleague suggested something along the lines of:

if(!lotsOfItems.All(x => x.ID != target.ID))

since this is supposed to stop once the conditions returns false for the first time but I'm not sure on that, so if anyone could shed some light on this as well it would be appreciated.

Answer 1

As we see from the source code, Yes:

 internal static bool Any<T>(this IEnumerable<T> source, Func<T, bool> predicate) {
            foreach (T element in source) {
                if (predicate(element)) {
                    return true; // Attention to this line
                }
            }
            return false;
        }

Any() is the most efficient way to determine whether any element of a sequence satisfies a condition with LINQ.

also:a colleague suggested something along the lines of

if(!lotsOfItems.All(x => x.ID != target.ID)) since this is supposed to stop once the conditions returns false for the first time but i'm not sure on that, so if anyone could shed some light on this as well it would be appreciated :>]

All() determines whether all elements of a sequence satisfy a condition. So, the enumeration of source is stopped as soon as the result can be determined.

Additional note:
The above is true if you are using Linq to objects. If you are using Linq to Database, then it will create a query and will execute it against database.

Answer 2

You could test it yourself: https://ideone.com/nIDKxr

public static IEnumerable<int> Tester()
{
    yield return 1;
    yield return 2;
    throw new Exception();
}

static void Main(string[] args)
{
    Console.WriteLine(Tester().Any(x => x == 1));
    Console.WriteLine(Tester().Any(x => x == 2));
    
    try
    {
        Console.WriteLine(Tester().Any(x => x == 3));
    }
    catch
    {
        Console.WriteLine("Error here");
    }
}

Yes, it does :-)

also:a colleague suggested something along the lines of

if(!lotsOfItems.All(x => x.ID != target.ID))

since this is supposed to stop once the conditions returns false for the first time but i'm not sure on that, so if anyone could shed some light on this as well it would be appreciated :>]

Using the same reasoning, All() could continue even if one of the element returns false :-) No, even All() is programmed correctly :-)