Can't add any new controllers to the existing web api2 project

Hi all, 

I have created a web api2 project and added my a controller call   : couple of days back  and all seems work ok, 

but  I just open up the same solution and added a new controller to the existing project and for some what reason what ever controller that I add,  and type the url its not working ,   still the original controller that i have added days back still works,  

below are the codes for the new controller that I have added today . which is not working 

public class TestingController : ApiController

{
// GET api/testing
public IHttpActionResult Get()
{
return Ok("Ok");
}

}

I am trying to access this controller like http://localhost:61202/Testing   and this is not working  for me  and always getting 

HTTP Error 404.0 - Not Found   error.

could some one let me know what sort of checks that I can do  ?