在MVC#中通过属性路由使用分页时，如何跳过可选的空参数？

我在控制器上的MVC 5应用程序中使用属性路由，该控制器用于获取列表并执行搜索、排序和分页：

    [HttpGet]    
    [Route("Admin/UserList/{searchBy?}/{search?}/{page?}/{sortBy?}")]  
    public ActionResult AdminUserList(string searchBy, string search, int? 
           page, string sortBy)
    {  
       IEnumerable<Employee> employees=new List<Employee>();
        string emailid=Session["EmailId"].ToString();
        var role = (from users in db.Employees where users.EmailId == 
         emailid select users.Role).SingleOrDefault();
        if (role==Roles.superAdmin)
        {
            employees = (from users in db.Employees where users.Role == 
            Roles.user || users.Role == Roles.admin select 
            users).AsEnumerable();

        }

        else
        {
            employees = (from users in db.Employees where users.Role == Roles.user select users).AsEnumerable();           
        }         
            ViewBag.NameSort = String.IsNullOrEmpty(sortBy) ? "Name desc" : ""; 


            if (searchBy == "Email ID")
            {
                employees = employees.Where(x => search == null || x.EmailId.Contains(search));
            }
            else
            {
                employees = employees.Where(x => search == null || x.Name.Contains(search));
            }

            switch (sortBy)
            {
                case "Name desc":
                    employees = employees.OrderByDescending(x => x.Name);
                    break;
                default:
                    employees = employees.OrderBy(x => x.Name);
                    break;
            }
            return View(employees.ToPagedList(page ?? 1, 6));              
    }

---

谢谢您的帮助。

只有最后一个参数可以标记为可选。如果有两个可选参数怎么办@StephenMueckei如果您有多个可选参数，那么路由引擎将始终生成查询字符串值，而不是路由值（除非提供了所有段）。它怎么可能是

Admin/UserList/X/Y

的url的意思呢？X是

searchBy

或

searchBy

或

page

或

sortBy

的值？如果您想要路由值，只有最后一个参数是可选的）好的，谢谢您的澄清@斯蒂芬穆克

@Html.PagedListPager(Model, page => Url.Action("UserList", new
   {
       page,
       searchBy = Request.QueryString["searchBy"],
       search = Request.QueryString["search"],
       sortBy = Request.QueryString["sortBy"]
    }),
      new PagedListRenderOptions() { Display = 
       PagedListDisplayMode.IfNeeded, DisplayPageCountAndCurrentLocation = 
      true })