>>>>>Hi,
>>>>>
>>>>>I created a HelloWorld Web API solution in VS 2013. I left all the code automatically created by VS unchanged.
>>>>>On executing of this project the VS opens the browser and puts the following URL: "localhost:53757" which shows a descriptive ASP.NET page created by VS.
>>>>>Then when I add "/api/values" to this URL making it "localhost:53757/api/values" and the browser returns the array of two values (from the Controller class).
>>>>>
>>>>>I would like to understand better the WebApiConfig class which is in the APP_START folder. This class calls method Register and passes the HttpConfiguration config. I have two questions, please:
>>>>>
>>>>>1. Do I understand correctly that this class (WebApiConfig) and method are called ONLY ONE TIME when you start the Web API (project)? Why I think so: I set a debug point in this class, and the debug point is hit only once when I execute the proejct. When I add the "/api/values" to the localhost:53757 (making it localhost:53757/api/value) code in the class WebApiConfig does not fire and debut point is not hit.
>>>>>
>>>>>2. Below is the code of the WebApiConfig class. Could someone please explain it - in English - as simply as possible (if possible).
>>>>>
>>>>>

>>>>>   public static class WebApiConfig
>>>>>    {
>>>>>        public static void Register(HttpConfiguration config)
>>>>>        {
>>>>>            // Web API configuration and services
>>>>>
>>>>>            // Web API routes
>>>>>            config.MapHttpAttributeRoutes();
>>>>>
>>>>>            config.Routes.MapHttpRoute(
>>>>>                name: "DefaultApi",
>>>>>                routeTemplate: "api/{controller}/{id}",
>>>>>                defaults: new { id = RouteParameter.Optional }
>>>>>            );
>>>>>        }
>>>>>    }
>>>>>

>>>>>
>>>>>Thank you in advance.
>>>>
>>>>Yup. Called only once to configure the routing for any subsequent webapi requests (that's why it's in the App_Start folder :-} )
>>>>
>>>>And, since you are using config.MapHttPAttributeRoutes() you shouldn't really need any other methods if you are using the RoutePrefix attribute on your ApiController and the Route attribute on the methods.
>>>
>>>Thank you for confirming my understanding on point 1.
>>>On point 2. I am using config.MapHttpAttributeRoutes() just because VS 2013 calls it (I really don't understand why). Is there a more up-to-date/better method to call?
>>
>>No - it is the more up-to-date method. The older way (using config.Routes.MapHttpRoute() was less flexible - especially with REST based services. Using attribute routing means that with something like this:

    [RoutePrefix("myController")]
>>    public class MyApiController : ApiController
>>    {
>>        [Route("doIt")]
>>        public HttpResponseMessage DoSomething()
>>        {
>>            return Request.CreateResponse(HttpStatusCode.OK, "Worked");
>>        }
>>    }

you call it with /myController/doIt
>>
>>See: https://docs.microsoft.com/en-us/aspnet/web-api/overview/web-api-routing-and-actions/attribute-routing-in-web-api-2
>
>Thank you again. I will have to study these concepts to understand them better. I have a question on the controller class but I will start a new thread on that.

Basically, rather than relying on routes configured manually using MapHttpRoute, with attribute routing the runtime 'parses' all the APIControllers and builds the routing tables from the attributes. You can also use attributes to define the methods (GET,POST,PUT etc) and accept verbs that a method will respond to.