I read a lot of post, and i dont see my mystake.
Can some body help me please.
There is my global.asax
public static void RegisterRoutes(RouteCollection routes)
        {
            routes.IgnoreRoute("{resource}.axd/{*pathInfo}");                
           routes.MapRoute(
                "Default",                                              // Route name
                "{controller}/{action}/{id}",                           // URL with parameters
                new { controller = "Home", action = "Index", id = "" }  // Parameter defaults
            );
           routes.MapRoute("UserName", "Account/{action}/{username}",
          new { action = "EditProfile", controller = "Account" });   
        }
        protected void Application_Start()
        {
            RegisterRoutes(RouteTable.Routes);
        }
When i use
<%= Html.ActionLink("Edit Account", "EditProfile", "Account", new { username = Html.Encode(Page.User.Identity.Name) },null) %>
I got this url
http://localhost:8458/Account/EditProfile?username=cboivin
if i try to call the url directly like http://localhost:8458/Account/EditProfile/cboivin
not work to ...
There is my method in my AccountController
 public ActionResult EditProfile(string username)
        {
            return View(ServiceFactory.UserAccount.GetUserByUserName(new GetUserByUserNameArgs(username)));
        }
I dont know where is my mistake. Can some body help me ? Thanks.