Question

I haven’t done much multithreading before and now find the need to do some background work and keep the UI responsive. I have the following code.

data.ImportProgressChanged += new 
     DataAccess.ImportDelegate(data_ImportProgressChanged);

Thread importThread = new Thread(
       new ThreadStart(data.ImportPeopleFromFAD));
importThread.IsBackground = true;
importThread.Start();

void data_ImportProgressChanged(int progress)
{
    toolStripProgressBar.Value = progress;
}

//In my data object I have 
public void ImportPeopleFromFAD()
{
    ImportProgressChanged(someInt);
}

But the UI doesn’t get updated since the ImportProgressChanged() call is made on the background thread. In objective C I know you can use performSelectorOnMainThread and pass it a method to call using the main thread. What is the equivalent way of calling ImportProgressChanged() from the main thread?

Answer 1

(Assuming Windows Forms.) You can use Control.Invoke or Control.BeginInvoke – but a cleaner way may be to use BackgroundWorker to start with.

In WPF you’d use a Dispatcher instead of Control.Invoke, btw. See this WPF threading model guide for more details.

EDIT: Personally I probably wouldn’t bother testing InvokeRequired first – I’d just call Invoke or BeginInvoke. If you’re already “on” the right thread it won’t do any significant harm.

For progress bars, however, BackgroundWorker is definitely the way forward.