启动后更改MVC6的路由集合

Question

在MVC-5中，我可以通过访问routetable在初始启动后编辑RouteTable.Routes。我希望在MVC-6中也这样做，这样我就可以在运行时添加/删除路由（对CMS很有用）。

在MVC-5中执行此操作的代码是：

using (RouteTable.Routes.GetWriteLock())
{
    RouteTable.Routes.Clear();

    RouteTable.Routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
    RouteTable.Routes.MapRoute(
        name: "Default",
        url: "{controller}/{action}/{id}",
        defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
    );
}

但我在MVC-6中找不到RouteTable.Routes或类似内容。知道如何在运行时更改路径集合吗？

我想在CMS中创建页面时使用此原则添加额外的URL。

如果您有类似的课程：

public class Page
{
    public int Id { get; set; }
    public string Url { get; set; }
    public string Html { get; set; }
}

和控制器一样：

public class CmsController : Controller
{
    public ActionResult Index(int id)
    {
        var page = DbContext.Pages.Single(p => p.Id == id);
        return View("Layout", model: page.Html);
    }
}

然后，当页面添加到数据库时，我重新创建routecollection：

var routes = RouteTable.Routes;
using (routes.GetWriteLock())
{
    routes.Clear();
    foreach(var page in DbContext.Pages)
    {
        routes.MapRoute(
            name: Guid.NewGuid().ToString(),
            url: page.Url.TrimEnd('/'),
            defaults: new { controller = "Cms", action = "Index", id = page.Id }
        );
    }

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

通过这种方式，我可以向CMS添加不属于约定或严格模板的页面。我可以添加一个包含网址/contact的网页，还可以添加一个包含网址/help/faq/how-does-this-work的网页。

Answer 1

答案是没有合理的方法来做到这一点，即使你找到了一种不太好的做法。

问题的错误方法

基本上，过去的MVC版本的路由配置意味着像DI配置一样 - 也就是说，您将所有内容放在composition root中，然后在运行时使用该配置。问题是你可以在运行时将对象推送到配置中（很多人都这样做了），这不是正确的方法。

现在配置已被真正的DI容器取代，这种方法将不再有效。注册步骤现在只能在应用程序启动时完成。

正确方法

自定义路由远远超出Route类在过去的MVC版本中可以执行的操作的正确方法是inherit RouteBase或路由。

MVC 6具有类似的抽象，IRouter和INamedRouter填充相同的角色。与其前身非常相似，IRouter只有两种方法可以实现。

namespace Microsoft.AspNet.Routing
{
    public interface IRouter
    {
        // Derives a virtual path (URL) from a list of route values
        VirtualPathData GetVirtualPath(VirtualPathContext context);

        // Populates route data (including route values) based on the
        // request
        Task RouteAsync(RouteContext context);
    }
}

此接口用于实现路由的双向特性 - URL用于路由值和路由值到URL。

示例：CachedRoute<TPrimaryKey>

这是一个跟踪和缓存主键到URL的1-1映射的示例。它是通用的，我测试过，无论主键是int还是Guid，它都能正常工作。

必须注入一个可插入的部分，ICachedRouteDataProvider可以实现数据库的查询。您还需要提供控制器和操作，因此该路由通用，足以通过使用多个实例将多个数据库查询映射到多个操作方法。

using Microsoft.AspNetCore.Routing;
using Microsoft.Extensions.Caching.Memory;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Threading.Tasks;

public class CachedRoute<TPrimaryKey> : IRouter
{
    private readonly string _controller;
    private readonly string _action;
    private readonly ICachedRouteDataProvider<TPrimaryKey> _dataProvider;
    private readonly IMemoryCache _cache;
    private readonly IRouter _target;
    private readonly string _cacheKey;
    private object _lock = new object();

    public CachedRoute(
        string controller, 
        string action, 
        ICachedRouteDataProvider<TPrimaryKey> dataProvider, 
        IMemoryCache cache, 
        IRouter target)
    {
        if (string.IsNullOrWhiteSpace(controller))
            throw new ArgumentNullException("controller");
        if (string.IsNullOrWhiteSpace(action))
            throw new ArgumentNullException("action");
        if (dataProvider == null)
            throw new ArgumentNullException("dataProvider");
        if (cache == null)
            throw new ArgumentNullException("cache");
        if (target == null)
            throw new ArgumentNullException("target");

        _controller = controller;
        _action = action;
        _dataProvider = dataProvider;
        _cache = cache;
        _target = target;

        // Set Defaults
        CacheTimeoutInSeconds = 900;
        _cacheKey = "__" + this.GetType().Name + "_GetPageList_" + _controller + "_" + _action;
    }

    public int CacheTimeoutInSeconds { get; set; }

    public async Task RouteAsync(RouteContext context)
    {
        var requestPath = context.HttpContext.Request.Path.Value;

        if (!string.IsNullOrEmpty(requestPath) && requestPath[0] == '/')
        {
            // Trim the leading slash
            requestPath = requestPath.Substring(1);
        }

        // Get the page id that matches.
        TPrimaryKey id;

        //If this returns false, that means the URI did not match
        if (!GetPageList().TryGetValue(requestPath, out id))
        {
            return;
        }

        //Invoke MVC controller/action
        var routeData = context.RouteData;

        // TODO: You might want to use the page object (from the database) to
        // get both the controller and action, and possibly even an area.
        // Alternatively, you could create a route for each table and hard-code
        // this information.
        routeData.Values["controller"] = _controller;
        routeData.Values["action"] = _action;

        // This will be the primary key of the database row.
        // It might be an integer or a GUID.
        routeData.Values["id"] = id;

        await _target.RouteAsync(context);
    }

    public VirtualPathData GetVirtualPath(VirtualPathContext context)
    {
        VirtualPathData result = null;
        string virtualPath;

        if (TryFindMatch(GetPageList(), context.Values, out virtualPath))
        {
            result = new VirtualPathData(this, virtualPath);
        }

        return result;
    }

    private bool TryFindMatch(IDictionary<string, TPrimaryKey> pages, IDictionary<string, object> values, out string virtualPath)
    {
        virtualPath = string.Empty;
        TPrimaryKey id;
        object idObj;
        object controller;
        object action;

        if (!values.TryGetValue("id", out idObj))
        {
            return false;
        }

        id = SafeConvert<TPrimaryKey>(idObj);
        values.TryGetValue("controller", out controller);
        values.TryGetValue("action", out action);

        // The logic here should be the inverse of the logic in 
        // RouteAsync(). So, we match the same controller, action, and id.
        // If we had additional route values there, we would take them all 
        // into consideration during this step.
        if (action.Equals(_action) && controller.Equals(_controller))
        {
            // The 'OrDefault' case returns the default value of the type you're 
            // iterating over. For value types, it will be a new instance of that type. 
            // Since KeyValuePair<TKey, TValue> is a value type (i.e. a struct), 
            // the 'OrDefault' case will not result in a null-reference exception. 
            // Since TKey here is string, the .Key of that new instance will be null.
            virtualPath = pages.FirstOrDefault(x => x.Value.Equals(id)).Key;
            if (!string.IsNullOrEmpty(virtualPath))
            {
                return true;
            }
        }
        return false;
    }

    private IDictionary<string, TPrimaryKey> GetPageList()
    {
        IDictionary<string, TPrimaryKey> pages;

        if (!_cache.TryGetValue(_cacheKey, out pages))
        {
            // Only allow one thread to poplate the data
            lock (_lock)
            {
                if (!_cache.TryGetValue(_cacheKey, out pages))
                {
                    pages = _dataProvider.GetPageToIdMap();

                    _cache.Set(_cacheKey, pages,
                        new MemoryCacheEntryOptions()
                        {
                            Priority = CacheItemPriority.NeverRemove,
                            AbsoluteExpirationRelativeToNow = TimeSpan.FromSeconds(this.CacheTimeoutInSeconds)
                        });
                }
            }
        }

        return pages;
    }

    private static T SafeConvert<T>(object obj)
    {
        if (typeof(T).Equals(typeof(Guid)))
        {
            if (obj.GetType() == typeof(string))
            {
                return (T)(object)new Guid(obj.ToString());
            }
            return (T)(object)Guid.Empty;
        }
        return (T)Convert.ChangeType(obj, typeof(T));
    }
}

CmsCachedRouteDataProvider

这是数据提供程序的实现，基本上是您在CMS中需要执行的操作。

public interface ICachedRouteDataProvider<TPrimaryKey>
{
    IDictionary<string, TPrimaryKey> GetPageToIdMap();
}

public class CmsCachedRouteDataProvider : ICachedRouteDataProvider<int>
{
    public IDictionary<string, int> GetPageToIdMap()
    {
        // Lookup the pages in DB
        return (from page in DbContext.Pages
                select new KeyValuePair<string, int>(
                    page.Url.TrimStart('/').TrimEnd('/'),
                    page.Id)
                ).ToDictionary(pair => pair.Key, pair => pair.Value);
    }
}

用法

这里我们在默认路由之前添加路由，并配置其选项。

// Add MVC to the request pipeline.
app.UseMvc(routes =>
{
    routes.Routes.Add(
        new CachedRoute<int>(
            controller: "Cms",
            action: "Index",
            dataProvider: new CmsCachedRouteDataProvider(), 
            cache: routes.ServiceProvider.GetService<IMemoryCache>(), 
            target: routes.DefaultHandler)
        {
            CacheTimeoutInSeconds = 900
        });

    routes.MapRoute(
        name: "default",
        template: "{controller=Home}/{action=Index}/{id?}");

    // Uncomment the following line to add a route for porting Web API 2 controllers.
    // routes.MapWebApiRoute("DefaultApi", "api/{controller}/{id?}");
});

这是它的要点。你仍然可以改善一些事情。

我个人会使用工厂模式并将存储库注入CmsCachedRouteDataProvider的构造函数，而不是在任何地方硬编码DbContext。

Answer 2

一种简单的方法是，如果发生404错误，则检查此问题：

如果路由列表中存在URL，则重定向至该地址

.net核心示例转到Startup.cs（项目根目录），然后在Configure方法中添加底部代码：

public void Configure(IApplicationBuilder app, IWebHostEnvironment env){
    app.UseStatusCodePages(async context =>
                    {
                        var redirctPage = pageToRedirect(context);
                        context.HttpContext.Response.Redirect(redirctPage);

                    }
...
}
    private string pageToRedirect(StatusCodeContext context)
    {
        var def = "";
        if(context.HttpContext.Response.StatusCode==404){
            if (context.HttpContext.Request.Path.ToString().ToLower().Contains("/product/"))
            {
                def = "/Home/Product";
                def += context.HttpContext.Request.QueryString;
            }
            else if (context.HttpContext.Request.Path.ToString().ToLower()=="/news")//or you can call class that load info from DB to redirect
            {
                def = "/Home/News";
                def += context.HttpContext.Request.QueryString;
            }
            else//404 error page
                def = "/Home/Error?statusCode=" + context.HttpContext.Response.StatusCode;
        }else //other errors code
            def = "/Home/Error?statusCode=" + context.HttpContext.Response.StatusCode;

        return def;
    }