Autofac with MVC4: controller does not have a default constructor
With the RegisterApiControllers method you tell Autofac where (in which assembly) it should look for your ApiControllers
So the following call:
builder.RegisterApiControllers(Assembly.GetExecutingAssembly());Registers the ApiControllers from the current assembly (project).
If you have ApiControllers also in a different project you need to use it like this:
builder.RegisterApiControllers(typeof(UserController).Assembly);Which means: register all the ApiController form the assembly (project) where the UserController lives. So you only need one RegisterApiControllers per assembly even if you have multiple ApiController in an assembly (project).