Question

Lets write simple console application:

    static void Main(string[] args)
    {
        IList<Thread> threads = new List<Thread>();
        Console.WriteLine((Process.GetCurrentProcess().Threads).OfType<ProcessThread>().Where(thread => thread.ThreadState == ThreadState.Wait).Count());
        for(int i=0;i<30;i++)
        {
            Thread t = new Thread(Test);
            Console.WriteLine("Before start: {0}", (Process.GetCurrentProcess().Threads).OfType<ProcessThread>().Where(thread => thread.ThreadState == ThreadState.Wait).Count());
            t.Start();
            Console.WriteLine("After start: {0}", (Process.GetCurrentProcess().Threads).OfType<ProcessThread>().Where(thread => thread.ThreadState == ThreadState.Wait).Count());
        }
        Console.WriteLine((Process.GetCurrentProcess().Threads).OfType<ProcessThread>().Where(thread => thread.ThreadState == ThreadState.Wait).Count());
        Console.ReadKey();
    }

    static void Test()
    {
        Thread.Sleep(0);
    }

As you see we created 30 waiting threads in our process. Where they are? MSDN:

Use ProcessThread to get all the threads associated with the current process.

Answer 1

Your threads exit nearly immediately. Sleep(0) isn’t a sleep forever, it’s just a yield. If there are no other runnable threads, the call to Sleep(0) just returns without yielding the timeslice. Your threads exit immediately after that call to Sleep.

Do a longer Sleep() to test this.