Question

I have method which create background thread to make some action. In this background thread I create object. But this object while creating in runtime give me an exception :

The calling thread must be STA, because many UI components require this.

I know that I must use Dispatcher to make reflect something to UI. But in this case I just create an object and dont iteract with UI. This is my code:

    public void SomeMethod()
      {
         BackgroundWorker worker = new BackgroundWorker();
         worker.DoWork += new DoWorkEventHandler(Background_Method);
         worker.RunWorkerAsync();
      }

   void Background_Method(object sender, DoWorkEventArgs e)
      {
         TreeView tv = new TreeView();
      }

How can I create objects in background thread?

I use WPF application

Answer 1

TreeView is a UI control. You can only create and manipulate UI controls on a UI thread, so what you’re trying to do is not possible.

What you want to do is do all of the time-consuming work on the background thread, and then “call back” to the UI thread to manipulate the UI. This is actually quite easy:

void Background_Method(object sender, DoWorkEventArgs e)
{
    // ... time consuming stuff...

    // call back to the window to do the UI-manipulation
    this.BeginInvoke(new MethodInvoker(delegate {
        TreeView tv = new TreeView();
        // etc, manipulate
    }));
}

I may have got the syntax wrong for BeginInvoke (it’s off the top of my head), but there you go anyway…