Code: C# Simple Multithreading Example using ThreadPool

Below you will find a simple, complete code sample for multithreading in C# using the ThreadPool class.  This sample uses a simple counter to track the number of threads that are active to prevent the application from closing before all threads have completed.  Although there are other ways to force a method to wait for all threads to complete before exiting, using a static counter allows you to create a separate method to determine when the application is allowed to exit.  This is useful for handling OnStop events on windows services.  Within the StopProcessing() method you could also set a flag that would prevent your application from creating new threads.

Code Snippet

1. using System;
2. using System.Collections.Generic;
3. using System.Linq;
4. using System.Text;
5. using System.Threading;
6.  
7. namespace MultiThreadedApp
8. {
9.     class Program
10.     {
11.         static int _threadCounter = 0;
12.  
13.         static void Main(string[] args)
14.         {
15.             for (int i = 0; i < 10; i++)
16.             {
17.                 CreateThread(i);
18.             }
19.  
20.             StopProcessing();
21.  
22.             Console.WriteLine("Finished");
23.         }
24.  
25.         private static void CreateThread(int threadId)
26.         {
27.             Console.WriteLine("Creating Thread {0}", threadId);
28.             MethodParameters newParameter = new MethodParameters();
29.             newParameter.ThreadId = threadId;
30.             newParameter.ThreadCreated = DateTime.Now;
31.             Interlocked.Increment(ref _threadCounter);
32.             ThreadPool.QueueUserWorkItem(new WaitCallback(LongRunningProcess), (object)newParameter);
33.         }
34.  
35.         private static void LongRunningProcess(object input)
36.         {
37.             MethodParameters inputParams = (MethodParameters)input;
38.             Random random = new Random(((MethodParameters)input).ThreadId);
39.             Thread.Sleep(random.Next(500, 5000));
40.             Console.WriteLine("Thread {0} complete in {1} seconds", inputParams.ThreadId,
41.                 (DateTime.Now - inputParams.ThreadCreated).TotalSeconds);
42.  
43.             Interlocked.Decrement(ref _threadCounter);
44.         }
45.  
46.         private static void StopProcessing()
47.         {
48.             Console.WriteLine("Waiting for {0} threads to complete", _threadCounter);
49.             while (_threadCounter > 0)
50.                 Thread.Sleep(500);
51.         }
52.  
53.         private class MethodParameters
54.         {
55.             public DateTime ThreadCreated { get; set; }
56.             public int ThreadId { get; set; }
57.         }
58.     }
59. }