The Background Worker

By Neelesh Vishwakarma May 07, 2013
Have a heavy task? Some have calculation to go with? UI blocks while doing it? Not to worry Background worker is there.

There are times when you need to do some heavy work. Of course there are times in every one's life when mom forces you to clean your room, but I am not talking about that “heavy” work, not now I mean. From heavy work I mean like when you need to iterate in a very large collection to make changes in its entities or something like that. If you are planning to do it in the main thread of Silverlight itself, then believe me buddy, you are in serious trouble. Doing that kind of stuff might block your user interface.

So here comes background worker in the picture. As the name itself suggests, background worker means…background worker. It is actually a thread with completed event. There are two basic events in Background worker that actually do work, yeah I mean literally,

  • DoWork
  • RunWorkerCompleted

are the two. DoWorker do the heavy lifting. RunWorkerCompleted is called when DoWorker completed doing heavy lifting. Let me first give you my mainpage.cs class which have Background worker initialized and its events created.

   1: public partial class MainPage : UserControl
   2: {
   3: readonly BackgroundWorker _bWorker = new BackgroundWorker();
   5: public MainPage() 
   6:     {
   7:         InitializeComponent();
   8:         _bWorker.DoWork += _bWorker_DoWork;
   9:         _bWorker.RunWorkerCompleted += _bWorker_RunWorkerCompleted;
  10:     }
  12: void _bWorker_DoWork(object sender, DoWorkEventArgs e)
  13:     {
  14: //Heavy lifting goes here
  15:     }
  17: void _bWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
  18:     {
  19: //When heavy lifting completed
  20:     }
  21: }

I have defined here, a read-only object of background worker _bWorker. The two events DoWork and RunWorkerCompleted, that we were talking about, are created in the constructor. I put my heavy code in the DoWork event, and code that is depended on the calculations returned from the heavy code will go into RunWorkerCompleted event. 
Background worker will not start doing work, not until you tell it to do so. And you can tell it by calling RunWorkerAsync() function.

In Xaml of my main page I have added a button, Do Work. Here is my page's xaml.

   1: <UserControl x:Class="Background.MainPage"
   2: xmlns=""
   3: xmlns:x=""
   4: xmlns:d=""
   5: xmlns:mc=""
   6: mc:Ignorable="d"
   7: d:DesignHeight="300" d:DesignWidth="400">
   9: <Grid x:Name="LayoutRoot" Background="White">
  10: <Button Content="Do Work" Width="150"
  11: Height="100" Click="ButtonBase_OnClick"/>
  12: </Grid>
  13: </UserControl>

And on the click even of the button:

   1: private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
   2: {
   3:    _bWorker.RunWorkerAsync();
   4: }

RunWorkerAsync function orders background worker to start doing task assigned, yes in the background, of course.