Single-threaded apartment - cannot instantiate ActiveX control

I need to get information about applied CSS styles in HTML page. I used AxWebBrowser and iterate IHTMLDOMNode. I'm able to get all the data I need and move the code into my application. The problem is that this part is running inside of the background worker and I got exception when trying to instantiate the control.

AxWebBrowser browser = new AxWebBrowser();

ActiveX control '8856f961-340a-11d0-a96b-00c04fd705a2' cannot be instantiated
because the current thread is not in a single-threaded apartment.

Is there any way how to solve this or other option than AxWebBrowser?

The problem you're running into is that most background thread / worker APIs will create the thread in a Multithreaded Apartment state. The error message indicates that the control requires the thread be a Single Threaded Apartment.

You can work around this by creating a thread yourself and specifying the STA apartment state on the thread.

var t = new Thread(MyThreadStartMethod);
t.SetApartmentState(ApartmentState.STA);
t.Start();

Go ahead and add [STAThread] to the main entry of your application, this indicates the COM threading model is single-threaded apartment (STA)

example:

static class Program
{
    /// <summary>
    /// The main entry point for the application.
    /// </summary>
    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new WebBrowser());
    }
}