How to Execute a Method Using the Thread Pool in C#?

Learn how to execute a task using a thread from the runtime’s thread pool.

First, Declare a method containing the code you want to execute.

The method’s signature must match that defined by the System.Threading.WaitCallback delegate.

It must return void and take a single object argument.

Call the static method QueueUserWorkItem of the System.Threading.ThreadPool class, passing it your method name.

The runtime will queue your method and execute it when a thread-pool thread becomes available.

The following example demonstrates how to use the ThreadPool class to execute a method named GetData.

using System;
using System.Threading;
namespace Thread_Pool_Demo
{
    class Program
    {
        public static void Main(string[] args)
        {
            // Execute GetData using the thread pool and no arguments.
            ThreadPool.QueueUserWorkItem(GetData);
            // Create a MessageInfo object to pass to the GetData method.
            Chat info = new Chat("Hi, thread pool example");
            // Set the max number of threads.
            ThreadPool.SetMaxThreads(2, 2);
            // Execute GetData using the thread pool and providing an
            // argument.
            ThreadPool.QueueUserWorkItem(GetData, info);
            // Wait to continue.
            Console.WriteLine("Main method complete. Press Enter.");
            Console.ReadLine();
        }
        public static void GetData(object state)
        {
            // Safely cast the state argument to a MessageInfo object.
            Chat config = state as Chat;
            // If the config argument is null, no arguments were passed to
            // the ThreadPool.QueueUserWorkItem method; use default values.
            if (config == null)
            {
                // Display a fixed message to the console three times.
                for (int count = 0; count < 3; count++)
                {
                    Console.WriteLine("A thread pool example " + count);
                    // Sleep for the purpose of demonstration. Avoid sleeping
                    // on thread-pool threads in real applications.
                    Thread.Sleep(TimeSpan.FromSeconds(2));
                }
            }
            else
            {
                for (int count = 0; count < 10; count++)
                {
                    Console.WriteLine(config.Message + " " + count);
                    // Sleep for the purpose of demonstration. Avoid sleeping
                    // on thread-pool threads in real applications.
                    Thread.Sleep(TimeSpan.FromSeconds(2));
                }
            }
        }
    }
    public class Chat
    {
        private string message;
        // A constructor that takes configuration settings for the thread.
        public Chat(string message)
        {
            this.message = message;
        }
        // Properties to retrieve configuration settings.
        public string Message { get { return message; } }
    }
}

Output