Web API enable attribute routing.

Web API uses Routing to matches a URI to an action. Attribute routing is the new type of routing in wen api 2.  As the name implies, attribute routing uses attributes to define routes. Attribute routing gives you more control over the URIs in your web API. 

[RoutePrefix("api/item")]
public class ItemController : ApiController
{
      [HttpGet]
      [Route("GetItems")]
      public IHttpActionResult GetItems()
      {
          return Ok();
      }
}

Enabling Attribute Routing:

To enable attribute routing, call MapHttpAttributeRoutes during configuration. This extension method is defined in the System.Web.Http.HttpConfigurationExtensions class.
using System.Web.Http;

namespace WebApplication
{
    public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
            // Web API routes
            config.MapHttpAttributeRoutes();

            // Other Web API configuration not shown.
        }
    }
}