.net - Single-threaded apartment - cannot instantiate ActiveX control

Question

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?

Answer 1

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();