Web API Routing MVC Back End

In the previous section, we learned that Web API can be configured in WebApiConfig class. Here, we will learn how to configure Web API routes.
Web API routing is similar to ASP.NET MVC Routing. It routes an incoming HTTP request to a particular action method on a Web API controller.
Web API supports two types of routing:
1. Convention-based Routing
2. Attribute Routing
Convention-based Routing
In the convention-based routing, Web API uses route templates to determine which controller and action method to execute. At least one route template must be added into route table in order to handle various HTTP requests.
When we created Web API project using WebAPI template in the Create Web API Project section, it also added WebApiConfig class in the App_Start folder with default route as shown below.
Example: WebApiConfig with Default Route
public static class WebApiConfig
public static void Register(HttpConfiguration config)
// Enable attribute routing
// Add default route using convention-based routing
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
In the above WebApiConfig.Register() method, config.MapHttpAttributeRoutes() enables attribute routing which we will learn later in this section. The config.Routes is a route table or route collection of type . The "DefaultApi" route is added in the route table using extension method. The MapHttpRoute() extension method internally creates a new instance of and adds it to an HttpRouteCollection. However, you can create a new route and add it into a collection manually as shown below.
Example: Add Default Route
public static class WebApiConfig
public static void Register(HttpConfiguration config)
// define route
IHttpRoute defaultRoute = config.Routes.CreateRoute("api/{controller}/{id}",
new { id = RouteParameter.Optional }, null);
// Add route
config.Routes.Add("DefaultApi", defaultRoute);
The following table lists parameters of MapHttpRoute() method.
Now, let's see how Web API handles an incoming http request and sends the response.
The following is a sample HTTP GET request.
Sample HTTP GET Request
GET http://localhost:1234/api/values/ HTTP/1.1
User-Agent: Fiddler
Host: localhost: 60464
Content-Type: application/json
Considering the DefaultApi route configured in the above WebApiConfig class, the above request will execute Get() action method of the ValuesController because HTTP method is a GET and URL is http://localhost:1234/api/values which matches with DefaultApi's route template /api/{controller}/{id} where value of {controller} will be ValuesController. Default route has specified id as an optional parameter so if an id is not present in the url then {id} will be ignored. The request's HTTP method is GET so it will execute Get() action method of ValueController.
If Web API framework does not find matched routes for an incoming request then it will send 404 error response.
The following figure illustrates Web API Routing.
Web API Routing
The following table displays which action method and controller will be executed on different incoming requests.
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