The parameters dictionary contains a null entry for parameter 'id' of non-nullable type 'System.Int32'
You are expecting an id parameter in your URL but you aren't supplying one. Such as:
http://yoursite.com/controller/edit/12
^^ missing
in your
WebApiConfig >> Register ()
You have to change to
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{action}/{id}",
defaults: new { id = RouteParameter.Optional }
Here the routeTemplate, is added with {action}