public interface IApplicationModelConvention
{
 void Apply(ApplicationModel application);
}
 

public class ApplicationModel : IPropertyModel, IFilterModel, IApiExplorerModel
{
 public ApiExplorerModel ApiExplorer { get; set; }
 public IList<ControllerModel> Controllers { get; }
 public IList<IFilterMetadata> Filters { get; }

 public IDictionary<object, object> Properties { get; }
}

//定义个类RouteConvention，来实现 IApplicationModelConvention 接口
public class RouteConvention : IApplicationModelConvention
{
 private readonly AttributeRouteModel _centralPrefix;

 public RouteConvention(IRouteTemplateProvider routeTemplateProvider)
 {
  _centralPrefix = new AttributeRouteModel(routeTemplateProvider);
 }

 //接口的Apply方法
 public void Apply(ApplicationModel application)
 {
  //遍历所有的 Controller
  foreach (var controller in application.Controllers)
  {
   // 已经标记了 RouteAttribute 的 Controller
   var matchedSelectors = controller.Selectors.Where(x => x.AttributeRouteModel != null).ToList();
   if (matchedSelectors.Any())
   {
    foreach (var selectorModel in matchedSelectors)
    {
     // 在 当前路由上 再 添加一个 路由前缀
     selectorModel.AttributeRouteModel = AttributeRouteModel.CombineAttributeRouteModel(_centralPrefix,
      selectorModel.AttributeRouteModel);
    }
   }

   // 没有标记 RouteAttribute 的 Controller
   var unmatchedSelectors = controller.Selectors.Where(x => x.AttributeRouteModel == null).ToList();
   if (unmatchedSelectors.Any())
   {
    foreach (var selectorModel in unmatchedSelectors)
    {
     // 添加一个 路由前缀
     selectorModel.AttributeRouteModel = _centralPrefix;
    }
   }
  }
 }
}

public static class MvcOptionsExtensions
{
 public static void UseCentralRoutePrefix(this MvcOptions opts, IRouteTemplateProvider routeAttribute)
 {
  // 添加我们自定义 实现IApplicationModelConvention的RouteConvention
  opts.Conventions.Insert(0, new RouteConvention(routeAttribute));
 }
}

public class Startup
{
 public Startup(IHostingEnvironment env)
 {
  //...
 }

 public void ConfigureServices(IServiceCollection services)
 {
  //...
  
  services.AddMvc(opt =>
  {
   // 路由参数在此处仍然是有效的，比如添加一个版本号
   opt.UseCentralRoutePrefix(new RouteAttribute("api/v{version}"));
  });
 }

 public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
 {
  //...
  
  app.UseMvc();
 }
}

[Route("order")]
public class OrderController : Controller
{
 // 路由地址 : /api/v{version}/order/details/{id}
 [Route("details/{id}")]
 public string GetById(int id, int version)
 {
  //上面是可以接收到版本号的，返回 version 和 id
  return $"other resource: {id}, version: {version}";
 }
}

public class ItemController : Controller
{
 // 路由地址： /api/v{version}/item/{id}
 [Route("item/{id}")]
 public string GetById(int id, int version)
 {
  //上面是可以接收到版本号的，返回 version 和 id
  return $"item: {id}, version: {version}";
 }
}