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  1. using System;
  2. using System.Linq;
  3. using System.Diagnostics;
  4. using System.Collections.Generic;
  5.  
  6. public class Test
  7. {
  8. 	class Point
  9. {
  10.     public int X { get; set; }
  11.     public int Y { get; set; }
  12. }
  13.  
  14. class Program
  15. {
  16.     static void Main()
  17.     {
  18.         var random = new Random();
  19.         List<Point> points = Enumerable.Range(0, 10000000).Select(x => new Point { X = random.Next(1000), Y = random.Next(1000) }).ToList();
  20.  
  21.   		int conditionValue = 250;
  22. 		Console.WriteLine($"Condition value: {conditionValue}");
  23.  
  24.         Stopwatch sw = new Stopwatch();
  25.         sw.Start();
  26.  
  27.         int hitCount1 = 0;
  28.         var points1 = points.Where(x =>
  29.         {
  30.             hitCount1++;
  31.             return x.X < conditionValue;
  32.         }).Select(x =>
  33.         {
  34.             hitCount1++;
  35.             return x.Y;
  36.         }).ToArray();
  37.  
  38.         sw.Stop();
  39.         Console.WriteLine($"Where -> Select: {sw.ElapsedMilliseconds} ms, {hitCount1} hits");
  40.  
  41.         sw.Restart();
  42.  
  43.         int hitCount2 = 0;
  44.         var points2 = points.Select(x =>
  45.         {
  46.             hitCount2++;
  47.             return x.Y;
  48.         }).Where(x =>
  49.         {
  50.             hitCount2++;
  51.             return x < conditionValue;
  52.         }).ToArray();
  53.  
  54.         sw.Stop();
  55.         Console.WriteLine($"Select -> Where: {sw.ElapsedMilliseconds} ms, {hitCount2} hits");
  56.  
  57.         Console.ReadLine();
  58.     }
  59. }
  60. }
Success #stdin #stdout 2.26s 30880KB
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stdin
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Standard input is empty
stdout
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Condition value: 250
Where -> Select: 266 ms, 12502408 hits
Select -> Where: 387 ms, 20000000 hits
https://ideone.com/jwZJLt
language:
C# (gmcs 5.20.1)
created:
7 years ago
visibility:
public

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