CODEWITHSUNDEEP
c#.netmultithreadingtimerthreadpool
vgorosh
vgorosh

Reputation: 35

Does System.Threading.Timer actually run in two different threads?

The code sample below

using System.Threading;

namespace TimerApp
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("***** Timer Application *****\n");
            Console.WriteLine("In the thread #{0}",     Thread.CurrentThread.ManagedThreadId); 

            // Create the delegate for the Timer type. 
            TimerCallback timerCB = new TimerCallback(ShowTime);

            // Establish timer settings. 
            Timer t = new Timer(
                timerCB,                // The TimerCallback delegate object. 
                "Hello from Main()",    // Any info to pass into the called method (null for no info). 
                0,                      // Amount of time to wait before starting (in milliseconds). 
                1000);                  // Interval of time between calls (in milliseconds). 

            Console.WriteLine("Hit key to terminate...");
            Console.ReadLine(); 
        }

        // Method to show current time... 
        public static void ShowTime(object state)
        {
        Console.WriteLine("From the thread #{0}, it is background?{1}: time is {2}, param is {3}", 
            Thread.CurrentThread.ManagedThreadId, 
            Thread.CurrentThread.IsBackground,
            DateTime.Now.ToLongTimeString(), 
            state.ToString()); 
        }
    }
 }

produces the following output

***** Timer Application *****

In the thread #1
Hit key to terminate...
From the thread #4, it is background?True: time is 10:37:54 PM, param is Hello from Main()
From the thread #4, it is background?True: time is 10:37:55 PM, param is Hello from Main()
From the thread #5, it is background?True: time is 10:37:56 PM, param is Hello from Main()
From the thread #4, it is background?True: time is 10:37:57 PM, param is Hello from Main()
From the thread #5, it is background?True: time is 10:37:58 PM, param is Hello from Main()
From the thread #4, it is background?True: time is 10:37:59 PM, param is Hello from Main()
From the thread #5, it is background?True: time is 10:38:00 PM, param is Hello from Main()
...
Press any key to continue . . .

Does the System.Threading.Timer make callbacks using several threads at a time?

Upvotes: 0

Views: 2461

Answers (1)

Aydin
Aydin

Reputation: 15324

It makes use of the thread pool, using the first thread that it finds available at each time interval. The timer simply triggers the firing of these threads.

void Main()
{
    System.Threading.Timer timer = new Timer((x) =>
    {
        Console.WriteLine($"{DateTime.Now.TimeOfDay} - Is Thread Pool Thread: {Thread.CurrentThread.IsThreadPoolThread} - Managed Thread Id: {Thread.CurrentThread.ManagedThreadId}");
        Thread.Sleep(5000);

    }, null, 1000, 1000);

    Console.ReadLine();
}

Output

07:19:44.2628607 - Is Thread Pool Thread: True - Managed Thread Id: 10
07:19:45.2639080 - Is Thread Pool Thread: True - Managed Thread Id: 13
07:19:46.2644998 - Is Thread Pool Thread: True - Managed Thread Id: 9
07:19:47.2649563 - Is Thread Pool Thread: True - Managed Thread Id: 8
07:19:48.2660500 - Is Thread Pool Thread: True - Managed Thread Id: 12
07:19:49.2664012 - Is Thread Pool Thread: True - Managed Thread Id: 14
07:19:50.2669635 - Is Thread Pool Thread: True - Managed Thread Id: 15
07:19:51.2679269 - Is Thread Pool Thread: True - Managed Thread Id: 10
07:19:52.2684307 - Is Thread Pool Thread: True - Managed Thread Id: 9
07:19:53.2693090 - Is Thread Pool Thread: True - Managed Thread Id: 13
07:19:54.2839838 - Is Thread Pool Thread: True - Managed Thread Id: 8
07:19:55.2844800 - Is Thread Pool Thread: True - Managed Thread Id: 12
07:19:56.2854568 - Is Thread Pool Thread: True - Managed Thread Id: 15

In the code above we are setting the thread to wait 5 seconds, so after printing out to the console, the thread is kept alive for an additional 5 seconds before completing execution and returning to the Thread Pool.

The timer carries on firing on each second regardless, it's not waiting on the thread it triggered to complete.

Upvotes: 4

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