What namespace does QuickBooks SDK 13.0 require to instantiate a QBSessionManager?

I have downloaded QuickBooks SDK 13.0 and am trying to create a very simple C # application that connects to QuickBooks

via QBSessionManager

.

I am using Visual Studio Express 2013. I have the following lines of code in the Load function of my very simple form.

QBSessionManager sessionManager = new QBSessionManager();
sessionManager.OpenConnection("", "Application");

      

        
        
        
      

    

When I try to compile I get

Could not find the type or namespace name 'QBSessionManager' (are you missing a using directive or an assembly reference?) "

I see a lot of code examples that start with instantiating QBSessionManager

, but nothing that identifies the namespace or reference that I need to provide.

Am I missing something really obvious?