ASP.NET MVC:带有可选参数的路由，但如果提供，则必须匹配 d+ [英] ASP.NET MVC: Route with optional parameter, but if supplied, must match d+

问题描述

我正在尝试编写一个包含可为空 int 的路由.应该可以同时访问 /profile/ 和 /profile/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+"});

如您所见，我说 userId 是可选的，但它也应该匹配正则表达式 d+.这不起作用，我明白为什么了.

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.

但是我如何构建一个既匹配 /profile/ 又匹配 /profile/ 后跟一个数字的路由?

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

推荐答案

最简单的 方法是添加另一个没有 userId 参数的路由，这样你就有了回退:

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，唯一可以做到这一点的方法是使用自定义约束.所以你的路线会变成:

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());

自定义约束代码将如下所示:

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 是这里最好的名字，但这取决于你！

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

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