Choosing between the any and exist methods in C#

Question

I want to check the inclusion of one list in another list.

my code

List<string> words = new(){"the","play","in","on"};
string txt="Barcelona is playing against Manchester tonight.";
    
List<string> txtList=txt.Split(' ', StringSplitOptions.RemoveEmptyEntries).ToList();
    
bool exist = false;
    
Stopwatch sw;
Stopwatch sw2;
    
sw = Stopwatch.StartNew();
for (int i=0; i<1000 ;i++)
{
    exist = words.Exists(w => txtList.Exists(t => t.Contains(w)));
}
sw.Stop();
Console.WriteLine("ExistResult: "+ exist + Environment.NewLine + "ExistTime: " + sw.ElapsedTicks);
    
    
sw2 = Stopwatch.StartNew();
for (int i=0; i<1000 ;i++)
{
    exist = words.Any(w => txtList.Any(t => t.Contains(w)));
}
sw2.Stop();
Console.WriteLine("AnyResult: "+ exist + Environment.NewLine + "AnyTime: " + sw2.ElapsedTicks);

Result

ExistResult: True

ExistTime: 2574053

AnyResult: True

AnyTime: 1265826

Method Any is twice as fast

But why does Visual Studio recommend that I use Exist method?

Answer 1

Benchmarking is hard, and you should never try to DYI your way to one. I couldn't even begin to tell you which of the million little rules you messed up, but a proper benchmark shows pretty much what you'd expect:

| Method | N     | Mean      | Error    | StdDev   |
|------- |------ |----------:|---------:|---------:|
| Exists | 1000  |  27.17 ms | 0.257 ms | 0.241 ms |
| Any    | 1000  |  53.19 ms | 0.614 ms | 0.575 ms |
| Exists | 5000  | 132.33 ms | 0.962 ms | 0.852 ms |
| Any    | 5000  | 259.50 ms | 1.104 ms | 0.979 ms |
| Exists | 10000 | 245.17 ms | 2.417 ms | 2.261 ms |
| Any    | 10000 | 521.30 ms | 4.468 ms | 4.179 ms |

In other words, Exists is about twice as fast as Any.