ASP.NET MVC：路线与可选参数，但如果提供，必须匹配\\ D + [英] ASP.NET MVC: Route with optional parameter, but if supplied, must match \d+

问题描述

我试着写在它可为空int类型的路线。应该可以去这两个 /型材/ 也 /型材/ \\ D + 。

I'm trying to write a route with a nullable int in it. It should be possible to go to both /profile/ but also /profile/\d+.

routes.MapRoute("ProfileDetails", "profile/{userId}",
                new {controller = "Profile",
                     action = "Details",
                     userId = UrlParameter.Optional},
                new {userId = @"\d+"});

正如你所看到的，我说，用户id 是可选的，但也是它应该匹配正前pression \\ D + 。这不工作，我知道为什么了。

As you can see, I say that userId is optional but also that it should match the regular expression \d+. This does not work and I see why.

不过，我将如何构建一个仅匹配 /型材/ 也 /型材/ 后跟一个路由号码是多少？

But how would I construct a route that matches just /profile/ but also /profile/ followed by a number?

推荐答案

的简单的方法是只需添加另一条路线，而不用户id 参数，让你有一个备用的：

The simplest way would be to just add another route without the userId parameter, so you have a fallback:

routes.MapRoute("ProfileDetails", "profile/{userId}",
                new {controller = "Profile",
                     action = "Details",
                     userId = UrlParameter.Optional},
                new {userId = @"\d+"});

routes.MapRoute("Profile", "profile",
                new {controller = "Profile",
                     action = "Details"});

据我所知，你能做到这一点的唯一的其他方式将是一个自定义的约束。所以，你的路线将变成：

As far as I know, the only other way you can do this would be with a custom constraint. So your route would become:

routes.MapRoute("ProfileDetails", "profile/{userId}",
                new {controller = "Profile",
                     action = "Details",
                     userId = UrlParameter.Optional},
                new {userId = new NullableConstraint());

和自定​​义约束code将是这样的：

And the custom constraint code will look like this:

using System;
using System.Web;
using System.Web.Routing;
using System.Web.Mvc;

namespace YourNamespace
{
    public class NullableConstraint : IRouteConstraint
    {
        public bool Match(HttpContextBase httpContext, Route route, string parameterName, RouteValueDictionary values, RouteDirection routeDirection)
        {
            if (routeDirection == RouteDirection.IncomingRequest && parameterName == "userId")
            {
                // If the userId param is empty (weird way of checking, I know)
                if (values["userId"] == UrlParameter.Optional)
                    return true;

                // If the userId param is an int
                int id;
                if (Int32.TryParse(values["userId"].ToString(), out id))
                    return true;
            }

            return false;
        }
    }
}

我不知道 NullableConstraint 是最好的名字在这里，但是这是给你的！

I don't know that NullableConstraint is the best name here, but that's up to you!

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