How to set Single Threaded Apartment model

[ProtocolPirate]

Somehow my project got into an MTA state, but I can't find a reference to MTA or STA anywhere in the entire solution. How do I set it back to STA?

 

[ProtocolPirate]

Also, when I try to bring up a dialog box from a class with no form, I get an exception of "control cannot be instantiated because the current thread is not in a single-threaded apartment". When I put <STAThread()> in front of the function that throws the exception, GetApartmentState still says MTA.

 

[ProtocolPirate]

I just discovered that from the main form GetApartmentState says STA, so somehow the formless class has been switched into an MTA state while the rest of the project is in an STA state.