ASP.NET 带有可选参数的 MVC 覆盖索引操作

Question

我想接受/User/和/User/213123

其中213123是参数(user_id)

这是我的RouteConfig.cs:

            routes.MapRoute(
                name: "user",
                url: "{controller}/{action}/{username}",
                defaults: new { controller = "User", action = "Index", username = UrlParameter.Optional }
            );

还有我的UserController.cs:

        public ActionResult Index()
        {
            ViewData["Message"] = "user index";
            return View();
        }

        [Route("user/{username}")]
        public ActionResult Index(string username)
        {
            ViewData["Message"] = "!" + username + "!";
            return View();
        }

这适用于 .net-core 1.0 但不适用于 mvc5。我错过了什么？

谢谢

编辑：

我的 UserController.cs 中只有这个也不起作用 (returns 404):

        public ActionResult Index(string username)
        {
            if (!String.IsNullOrEmpty(username))
            {
                ViewData["Message"] = "Hello " + username;
            }
            else
            {
                ViewData["Message"] = "user index";
            }

            return View();
        }

Description: HTTP 404. The resource you are looking for (or one of its dependencies) could have been removed, had its name changed, or is temporarily unavailable. Please review the following URL and make sure that it is spelled correctly.

Requested URL: /user/asd

编辑 2：

已更新RouteConfig.cs:

        routes.MapRoute(
            "userParam", "user/{username}",
          new { controller = "user", action = "IndexByUsername" },
          new { username = @"\w+" }
        );

        routes.MapRoute(
            name: "user",
            url: "user",
            defaults: new { controller = "User", action = "Index"}
        );

/User/ 现在以 Index 作为用户名

调用 IndexByUsername

/User/asd还是returns404

EDIT4：当前代码：

RouteConfig.cs:

routes.MapRoute(
            name: "Default",
            url: "{controller}/{action}/",
            defaults: new { controller = "Home", action = "Index" }
        );
routes.MapRoute("userParam", "user/{username}", new { controller = "user", action = "Index"});
routes.MapRoute("user", "{controller}/{action}/{username}", new { controller = "User", action = "Index", username = UrlParameter.Optional });

UserController.cs:

public class UserController : Controller
{
    public ActionResult Index(string username)
    {
        if (!String.IsNullOrEmpty(username))
        {
            ViewData["Message"] = "Hello " + username;
        }
        else
        {
            ViewData["Message"] = "user index";
        }

        return View();
    }
}

Answer 1

您只需要一个带有签名的操作方法

public ActionResult Index(string username)

并且在该方法中，您可以检查 username 的值是否为 null。

然后你的路由定义需要是（注意user路由需要放在默认路由之前）

routes.MapRoute(
    name: "user",
    url: "user/{username}",
    defaults: new { controller = "User", action = "Index", username = UrlParameter.Optional }
);
routes.MapRoute(
    name: "Default",
    url: "{controller}/{action}/{id}",
    defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
);

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