LINQ .Any VS .Exists - What's the difference?

See documentation

List.Exists (Object method - MSDN)

Determines whether the List(T) contains elements that match the conditions defined by the specified predicate.

This exists since .NET 2.0, so before LINQ. Meant to be used with the Predicate delegate, but lambda expressions are backward compatible. Also, just List has this (not even IList)

IEnumerable.Any (Extension method - MSDN)

Determines whether any element of a sequence satisfies a condition.

This is new in .NET 3.5 and uses Func(TSource, bool) as argument, so this was intended to be used with lambda expressions and LINQ.

In behaviour, these are identical.

The difference is that Any is an extension method for any IEnumerable<T> defined on System.Linq.Enumerable. It can be used on any IEnumerable<T> instance.

Exists does not appear to be an extension method. My guess is that coll is of type List<T>. If so Exists is an instance method which functions very similar to Any.

In short, the methods are essentially the same. One is more general than the other.

• Any also has an overload which takes no parameters and simply looks for any item in the enumerable.
• Exists has no such overload.

As a continuation on Matas' answer on benchmarking.

TL/DR: Exists() and Any() are equally fast.

First off: Benchmarking using Stopwatch is not precise (see series0ne's answer on a different, but similiar, topic), but it is far more precise than DateTime.

The way to get really precise readings is by using Performance Profiling. But one way to get a sense of how the two methods' performance measure up to each other is by executing both methods loads of times and then comparing the fastest execution time of each. That way, it really doesn't matter that JITing and other noise gives us bad readings (and it does), because both executions are "equally misguiding" in a sense.

static void Main(string[] args)
    {
        Console.WriteLine("Generating list...");
        List<string> list = GenerateTestList(1000000);
        var s = string.Empty;

        Stopwatch sw;
        Stopwatch sw2;
        List<long> existsTimes = new List<long>();
        List<long> anyTimes = new List<long>();

        Console.WriteLine("Executing...");
        for (int j = 0; j < 1000; j++)
        {
            sw = Stopwatch.StartNew();
            if (!list.Exists(o => o == "0123456789012"))
            {
                sw.Stop();
                existsTimes.Add(sw.ElapsedTicks);
            }
        }

        for (int j = 0; j < 1000; j++)
        {
            sw2 = Stopwatch.StartNew();
            if (!list.Exists(o => o == "0123456789012"))
            {
                sw2.Stop();
                anyTimes.Add(sw2.ElapsedTicks);
            }
        }

        long existsFastest = existsTimes.Min();
        long anyFastest = anyTimes.Min();

        Console.WriteLine(string.Format("Fastest Exists() execution: {0} ticks\nFastest Any() execution: {1} ticks", existsFastest.ToString(), anyFastest.ToString()));
        Console.WriteLine("Benchmark finished. Press any key.");
        Console.ReadKey();
    }

    public static List<string> GenerateTestList(int count)
    {
        var list = new List<string>();
        for (int i = 0; i < count; i++)
        {
            Random r = new Random();
            int it = r.Next(0, 100);
            list.Add(new string('s', it));
        }
        return list;
    }

After executing the above code 4 times (which in turn do 1 000 Exists() and Any() on a list with 1 000 000 elements), it's not hard to see that the methods are pretty much equally fast.

Fastest Exists() execution: 57881 ticks
Fastest Any() execution: 58272 ticks

Fastest Exists() execution: 58133 ticks
Fastest Any() execution: 58063 ticks

Fastest Exists() execution: 58482 ticks
Fastest Any() execution: 58982 ticks

Fastest Exists() execution: 57121 ticks
Fastest Any() execution: 57317 ticks

There is a slight difference, but it's too small a difference to not be explained by background noise. My guess would be that if one would do 10 000 or 100 000 Exists() and Any() instead, that slight difference would disappear more or less.

Additionally, this will only work if Value is of type bool. Normally this is used with predicates. Any predicate would be generally used find whether there is any element satisfying a given condition. Here you're just doing a map from your element i to a bool property. It will search for an "i" whose Value property is true. Once done, the method will return true.