Question

I have written a sample program below.

class Program
    {
        static int x = 2;

        static void Main(string[] args)
        {
            Console.WriteLine("Thread ID {0} and Main Called!", Thread.CurrentThread.ManagedThreadId);

            ThreadPool.QueueUserWorkItem(Count, args);
            ThreadPool.QueueUserWorkItem(Count2, args);

            Console.WriteLine("Thread ID {0} and Main Done!", Thread.CurrentThread.ManagedThreadId);
            Console.ReadLine();
        }
        static void Count(object args)
        { 
            for (int i = 0; i < 10; i++)
            {
                x = x + 2;
                Console.WriteLine("Thread ID {0} AND Count 1: " + x, Thread.CurrentThread.ManagedThreadId);
            }
        }
        static void Count2(object args)
        {
            for (int i = 0; i < 10; i++)
            {
                x = x + 2;
                Console.WriteLine("Thread ID {0} AND Count 2: " + x, Thread.CurrentThread.ManagedThreadId);
            }
        }
    }

When calling the Count method using ThreadPool.QueueUserWorkItem, I noticed that Main is finished before the Count method completes and Count2 method gets tangled up with Count Method.

Is there anyway for Main (and Count2) to wait until the Count method has compleleted? I do not want to use a lock nor Thread.Sleep (since I dont know how long the Count operations will take). I have read somewhere async calls or WAIT is used for this time of situations.

Any ideas?

Answer 1

I think AutoResetEvent is what you are after

**EDIT: **
Here is the modified code (untested). I used AutoResetEvent rather than Manual in this example

class Program
{
    static int x = 2;
    // Define an array with two AutoResetEvent WaitHandles.
    static WaitHandle[] waitHandles = new WaitHandle[] 
    {
        new AutoResetEvent(false),
        new AutoResetEvent(false)
    };



    static void Main(string[] args)
    {
        Console.WriteLine("Thread ID {0} and Main Called!", Thread.CurrentThread.ManagedThreadId);

        ThreadPool.QueueUserWorkItem(new WaitCallback(Count), waitHandles[0]);
        ThreadPool.QueueUserWorkItem(new WaitCallback(Count2), waitHandles[1]);
        WaitHandle.WaitAll(waitHandles);


        Console.WriteLine("Thread ID {0} and Main Done!", Thread.CurrentThread.ManagedThreadId);
        Console.ReadLine();
    }
    static void Count(object args)
    {
        AutoResetEvent are = (AutoResetEvent)args;

        for (int i = 0; i < 10; i++)
        {
            x = x + 2;
            Console.WriteLine("Thread ID {0} AND Count 1: " + x, Thread.CurrentThread.ManagedThreadId);
        }
        are.Set();

    }
    static void Count2(object args)
    {
        AutoResetEvent are = (AutoResetEvent)args;

        for (int i = 0; i < 10; i++)
        {
            x = x + 2;
            Console.WriteLine("Thread ID {0} AND Count 2: " + x, Thread.CurrentThread.ManagedThreadId);
        }
        are.Set();
    }
}