Foreach loop vs Parallel.ForEach

Foreach loop:

·         Iterations takes place sequentially one by one

·         foreach loop is run from a single Thread.

·         foreach loop is defined in every framework of .NET

·         Execution is slower

Parallel.ForEach:

·         Execution takes place in parallel way.

·         Parallel.ForEach uses multiple Threads.

·         Parallel.ForEach is defined in .Net 4.0 and above frameworks.

·         Execution is faster3

The following example clearly demonstrates the difference between traditional foreach loop and

Parallel.ForEach() Example.

using System;

    using System.Diagnostics;

    using System.Threading;

    using System.Threading.Tasks;

    namespace ParallelForEachExample

    {

        class Program

        {

            static void Main()

            {

                string[] colors = {

                                      "1. Red",

                                      "2. Green",

                                      "3. Blue",

                                      "4. Yellow",

                                      "5. White",

                                      "6. Black",

                                      "7. Violet",

                                      "8. Brown",

                                      "9. Orange",

                                      "10. Pink"

                                  };

                Console.WriteLine("Traditional foreach loop\n");

                //start the stopwatch for "for" loop

                var sw = Stopwatch.StartNew();

                foreach (string color in colors)

                {

                    Console.WriteLine("{0}, Thread Id= {1}", color, Thread.CurrentThread.ManagedThreadId);

                    Thread.Sleep(10);

                }

                Console.WriteLine("foreach loop execution time = {0} seconds\n", sw.Elapsed.TotalSeconds);

                Console.WriteLine("Using Parallel.ForEach");

                //start the stopwatch for "Parallel.ForEach"

                 sw = Stopwatch.StartNew();

                Parallel.ForEach(colors, color =>

                {

                    Console.WriteLine("{0}, Thread Id= {1}", color, Thread.CurrentThread.ManagedThreadId);

                    Thread.Sleep(10);

                }

                );

                Console.WriteLine("Parallel.ForEach() execution time = {0} seconds", sw.Elapsed.TotalSeconds);

                Console.Read();

            }

        }

    }

Traditional foreach loop

1. Red, Thread Id= 10

2. Green, Thread Id= 10

3. Blue, Thread Id= 10

4. Yellow, Thread Id= 10

5. White, Thread Id= 10

6. Black, Thread Id= 10

7. Violet, Thread Id= 10

8. Brown, Thread Id= 10

9. Orange, Thread Id= 10

10. Pink, Thread Id= 10

foreach loop execution time = 0.1054376 seconds

1. Red, Thread Id= 10

3. Blue, Thread Id= 11

4. Yellow, Thread Id= 11

2. Green, Thread Id= 10

5. White, Thread Id= 12

7. Violet, Thread Id= 14

9. Orange, Thread Id= 13

6. Black, Thread Id= 11

8. Brown, Thread Id= 10

10. Pink, Thread Id= 12

Parallel.ForEach() execution time = 0.055976 seconds