How BackgroundWorker Works

I've decided to take a deeper look at all available multi-threading options in .net 4.5. One of the simpler options is the BackgroundWorker. To investigate, I've setup a simple BackgroundWorker with progress and completion reporting.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ComponentModel;
using System.Threading;

namespace TestBackgroundWorker
{
    class TestBkGrdWorker
    {
        private void LogMsg(string msg)
        {
            Console.Out.WriteLine("{0} ThreadId={1}, {2}",
                DateTime.Now.ToString("HH:MM:ss.fff"),
                Thread.CurrentThread.ManagedThreadId, msg);
        }


        // RunTest
        //
        // Function run by main thread
        // Main thread sets up the background worker instance
        // and fires it off

        public void RunTest()
        {
            BackgroundWorker bkWorker = new BackgroundWorker();
            bkWorker.WorkerReportsProgress = true;  

            // setup functions the background worker calls
            // to do work, report progress, and to report completion
            bkWorker.DoWork += bkWorker_DoWork;
            bkWorker.ProgressChanged += bkWorker_ProgressChanged;
            bkWorker.RunWorkerCompleted += bkWorker_RunWorkerCompleted;

            // trigger background worker to run async
            bkWorker.RunWorkerAsync();

            // main thread do something while background worker do something else
            for (int i = 0; i < 5; i++)
            {
                LogMsg(string.Format("Main thread working, BackgroundWorker busy={0}",
                    bkWorker.IsBusy));
                Thread.Sleep(1000);
            }
        }


        // bkWorker_ProgressChanged
        //
        // Report progress

        void bkWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            LogMsg(string.Format("Background worker update progress, {0:00.0}% done", 
                e.ProgressPercentage));
        }

        // bkWorker_RunWorkerCompleted
        // 
        // Report work is completed

        void bkWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            LogMsg("Background worker completed");
        }

        
        // bkWorker_DoWork
        // 
        // Function run by background worker.
        // Random work method that takes an arbitrarily set 2 seconds
        // to complete, with a progress report every 200ms.

        void bkWorker_DoWork(object sender, DoWorkEventArgs e)
        {
            LogMsg("Background worker starting");

            float percentDone = 0.0f;
            for (int i = 0; i < 10; i++)
            {
                Thread.Sleep(200);
                percentDone += 10.0f;
                BackgroundWorker bkwkr = sender as BackgroundWorker;
                if (bkwkr != null)
                {
                    bkwkr.ReportProgress((int)percentDone);
                }
            }
            LogMsg("Background worker completed");
        }


        // Main
        // Start up a background worker test instance

        static void Main(string[] args)
        {
            TestBkGrdWorker testWkr = new TestBkGrdWorker();
            testWkr.RunTest();
        }
    }
}

The output looks as follows:

 12:12:04.680 ThreadId=3, Background worker starting
 12:12:04.680 ThreadId=1, Main thread working, BackgroundWorker busy=True
 12:12:04.945 ThreadId=4, Background worker update progress, 10.0% done
 12:12:05.148 ThreadId=4, Background worker update progress, 20.0% done
 12:12:05.350 ThreadId=4, Background worker update progress, 30.0% done
 12:12:05.553 ThreadId=4, Background worker update progress, 40.0% done
 12:12:05.756 ThreadId=4, Background worker update progress, 50.0% done
 12:12:05.756 ThreadId=1, Main thread working, BackgroundWorker busy=True
 12:12:05.959 ThreadId=4, Background worker update progress, 60.0% done
 12:12:06.162 ThreadId=4, Background worker update progress, 70.0% done
 12:12:06.364 ThreadId=4, Background worker update progress, 80.0% done
 12:12:06.567 ThreadId=4, Background worker update progress, 90.0% done
 12:12:06.770 ThreadId=3, Background worker completed
 12:12:06.770 ThreadId=3, Background worker update progress, 100.0% done
 12:12:06.770 ThreadId=4, Background worker completed
 12:12:06.770 ThreadId=1, Main thread working, BackgroundWorker busy=True
 12:12:07.784 ThreadId=1, Main thread working, BackgroundWorker busy=False
 12:12:08.798 ThreadId=1, Main thread working, BackgroundWorker busy=False