using System;

using System.Collections.Generic;

using System.Diagnostics;

using System.Linq;

List<string> strings = new List<string>();

​

for (int i = 0; i < 10000; i++)

{

    strings.Add($"string {i}");

}

​

Stopwatch _stopwatch2 = new Stopwatch();

​

_stopwatch2.Start();

foreach (var @string in strings)

{

    var count = strings.Count(x => x.StartsWith('1'));

}

_stopwatch2.Stop();

​

Console.WriteLine(_stopwatch2.ElapsedMilliseconds);

Stopwatch _stopwatch = new Stopwatch();

​

_stopwatch.Start();

foreach (var @string in strings)

{

    var count = strings.Where(x => x.StartsWith('1')).Count();

}

_stopwatch.Stop();

​

Console.WriteLine(_stopwatch.ElapsedMilliseconds);