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

As mentioned here[^]: 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();

More discussions here:
Discussion 1[^]
Discussion 2[^]
internal exception in this code[^]