这另一个潜在原因是，如果

Another potential reason for this is if the

    GlobalConfiguration.Configure(WebApiConfig.Register);

是在

    RouteConfig.RegisterRoutes(RouteTable.Routes);

在的global.asax.cs

in global.asax.cs

它需要之前，否则默认RouteConfig路线'吃'的路线的WebAPI - 并试图映射API请求到一个控制器称为API ...

It needs to be before, otherwise the default RouteConfig route 'eats' the WebAPI route - and attempts to map API requests to a controller called API...