Re: [ADVANCED-DOTNET] Question about the right way to use BackGroundWorker

[Nassar, Anthony]

Ryan, couldn't you just use the InterlockedBlah methods to save yourself
from having to lock? 

-----Original Message-----
From: Discussion of advanced .NET topics.
[mailto:[EMAIL PROTECTED] On Behalf Of Ryan Heath
Sent: Friday, July 20, 2007 4:37 AM
To: ADVANCED-DOTNET@DISCUSS.DEVELOP.COM
Subject: Re: [ADVANCED-DOTNET] Question about the right way to use
BackGroundWorker

I have added a simple class CountedEvent to your code [1] Now you do not
have to burn the cpu waiting for all jobs to finish.

Its interesting to see that RunWorkerCompleted is called after(!) all
jobs have finished... This is due to that BackgroundWorker is designed
to work in an UI environment. When no real UI response is needed the
BackgroundWorker would not be my first choice for this kind of work. I
supports Gregs suggestion to use QueueUserWorkItem, and perhaps in
combination with CountedEvent.

HTH
// Ryan

[1]
using System;
using System.Collections.Generic;
using System.Text;
using System.ComponentModel;
using System.Threading;
using System.Collections;

namespace BackgroundWorkerDemo
{
    class CountedEvent
        {
          ManualResetEvent evt = new ManualResetEvent(true);
          int calls = 0;

          public void WaitOne()
          {
            evt.WaitOne();
          }
          public void Set()
          {
            lock( evt)
                {
                  calls--;
              if ( calls == 0)
                  {
                    evt.Set();
                  }
                }
          }
          public void Reset()
          {
                lock( evt)
                {
                  if ( calls == 0)
                  {
                    evt.Reset();
                  }
                  calls++;
                }
          }
        }

   class Program
   {
       static void Main(string[] args)
       {
           DateTime start_time = DateTime.Now;

           Console.WriteLine("Program starting");

           //RunSyncVersion();
           RunAsyncVersion();

           DateTime end_time = DateTime.Now;

           TimeSpan ts = end_time - start_time;

           Console.WriteLine("Program completed. Duration={0} seconds.",
ts.Seconds);
           Console.Read();
       }

       //Synchronous version
       static void RunSyncVersion()
       {
           for (int i = 0; i <= 10; i++)
           {
               LongRunningOperation(i);
           }
       }

       //This version uses the async version
       static void RunAsyncVersion()
       {
                        CountedEvent jobFinished = new CountedEvent();
           ArrayList lstBGWs = new ArrayList();

           for (int i = 0; i <= 10; i++)
           {
               BackgroundWorker worker = new BackgroundWorker();
                                jobFinished.Reset();

               worker.DoWork += new DoWorkEventHandler(worker_DoWork);

               worker.RunWorkerCompleted += delegate(object sender,
RunWorkerCompletedEventArgs e)
                        {
                                        jobFinished.Set();
                        Console.WriteLine("Set called");
                        };

               lstBGWs.Add(worker);

               worker.RunWorkerAsync(i);
           }

                        jobFinished.WaitOne();
                        Console.WriteLine("exit");
       }

       static void worker_DoWork(object sender, DoWorkEventArgs e)
       {
           BackgroundWorker worker = sender as BackgroundWorker;

           LongRunningOperation(Convert.ToInt32(e.Argument));
       }

       //Long running operation
       private static void LongRunningOperation(int operation_number)
       {
           Console.WriteLine("Operation# {0} starting on Thread {1}",
operation_number, Thread.CurrentThread.ManagedThreadId);
           for (int i=0; i < 1000000000; i++)
           {

           }

           Console.WriteLine("Finished operation# {0} on Thread {1}",
operation_number, Thread.CurrentThread.ManagedThreadId);

       }
   }
}

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