c# - 为什么 MVC 5 不调用我的 VirtualPathProvider 类的 GetFile 方法？

Question

我正在尝试从数据库加载 Razor View。

我关注 ASP.NET MVC and virtual views和 VirtualPathProvider in MVC 5这样做。

我的代码:

虚拟路径提供者:

 public class DbPathProvider : VirtualPathProvider
  {
    public override bool FileExists(string virtualPath)
    {
        var page = FindPage(virtualPath);
        if (page == null)
        {
            return base.FileExists(virtualPath);
        }
        else
        {
            return true;
        }
    }

    public override VirtualFile GetFile(string virtualPath)
    {
        var page = FindPage(virtualPath);
        if (page == null)
        {
            return base.GetFile(virtualPath);
        }
        else
        {
            return new DbVirtualFile(virtualPath, page.PageData.ToArray());
        }
    }

    private SiteModel FindPage(string virtualPath)
    {
        var db = new DatabaseContext();
        var page = db.SiteModels.FirstOrDefault(x => x.SiteName == virtualPath);
        return page;
    }
}

虚拟文件

public class DbVirtualFile : VirtualFile
{
    private byte[] data;

    public DbVirtualFile(string virtualPath, byte[] data)
        : base(virtualPath)
    {
        this.data = data;
    }

    public override System.IO.Stream Open()
    {
        return new MemoryStream(data);
    }
}

全局.asax:

protected void Application_Start()
    {
        HostingEnvironment.RegisterVirtualPathProvider(new DbPathProvider());
        AreaRegistration.RegisterAllAreas();
        FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
        RouteConfig.RegisterRoutes(RouteTable.Routes);
        BundleConfig.RegisterBundles(BundleTable.Bundles);

    }

行动:

public ActionResult Display(string id)
    {
        var db = new DatabaseContext();
        var site = db.SiteModels.FirstOrDefault(x => x.PageName == id);
        if (site == null)
        {
            return RedirectToAction("Index", "Home");
        }
        ViewBag.Body = site.PageContent;
        return View(System.IO.Path.GetFileNameWithoutExtension(site.SiteName));
    }

数据:

案例一:

当 virtualPath 值为 "/Views/Home/Contact.cshtml" 时，FileExists 方法返回 true 并调用 GetFile 方法。

案例二:

当 virtualPath 值为 "~/Home/Display/ce28bbb6-03cb-4bf4-8820-373890396a90" 时，FileExists 方法返回 true 和 GetFile 方法和永远不会调用显示操作。 结果是

HTTP 错误 404.0 - 未找到您要查找的资源已被删除、更名或暂时不可用。

我不知道动态 View 。我刚刚阅读了那两篇文章并尝试实现它。

请告诉我哪里做错了。

我正在使用 MVC 5 和 .NET 4.5

Answer 1

有些事情我应该可以帮助你。有一些你没有考虑的事情没关系，因为我也遇到过很多麻烦。

我认为您在这里遇到的问题是了解所有内容的触发顺序。这是发生了什么:

1. 首先调用 VirtualPathProvider FileExists 方法并这是您施展魔法寻找页面的地方。我的方法和你的略有不同，这里是一个例子:

   public IList<Page> Pages
   {
       get
       {
           using (var uow = new UnitOfWork<SkipstoneContext>())
           {
               var companyService = new CompanyService(uow);
               var company = companyService.GetTenant();
   
               if (company != null)
               {
                   var pageService = new PageService(uow, company.Id);
   
                   return pageService.GetPublished();
               }
           }
   
           return null;
       }
   }
   
   public override bool FileExists(string virtualPath)
   {
       if (IsVirtualPath(virtualPath))
       {
           if (FindPage(virtualPath) != null)
           {
               var file = (PageVirtualFile)GetFile(virtualPath);
               return file.Exists;
           }
       }
   
       return Previous.FileExists(virtualPath);
   }
   
   public override VirtualFile GetFile(string virtualPath)
   {
       if (IsVirtualPath(virtualPath))
       {
           var page = FindPage(virtualPath);
           if (page != null)
           {
               var decodedString = Uri.UnescapeDataString(page.ViewData);
               var bytes = Encoding.ASCII.GetBytes(decodedString);
   
               return new PageVirtualFile(virtualPath, bytes);
           }
       }
   
       return Previous.GetFile(virtualPath);
   }
   
   public override System.Web.Caching.CacheDependency GetCacheDependency(string virtualPath, System.Collections.IEnumerable virtualPathDependencies, DateTime utcStart)
   {
       if (IsVirtualPath(virtualPath))
           return null;
   
       return Previous.GetCacheDependency(virtualPath, virtualPathDependencies, utcStart);
   }
   
   public override string GetFileHash(string virtualPath, System.Collections.IEnumerable virtualPathDependencies)
   {
       if (IsVirtualPath(virtualPath))
           return Guid.NewGuid().ToString();
   
       return Previous.GetFileHash(virtualPath, virtualPathDependencies);
   }
   
   private Page FindPage(string virtualPath)
   {
       var virtualName = VirtualPathUtility.GetFileName(virtualPath);
       var virtualExtension = VirtualPathUtility.GetExtension(virtualPath);
   
       try
       {
           if (Pages != null)
           {
               var id = Convert.ToInt32(virtualName.Replace(virtualExtension, ""));
               var page = Pages.Where(model => model.Id == id && model.Extension.Equals(virtualExtension, StringComparison.OrdinalIgnoreCase)).SingleOrDefault();
   
               return page;
           }
       }
       catch(Exception ex)
       {
           // Do nothing
       }
   
       return null;
   }
   
   private bool IsVirtualPath(string virtualPath)
   {
       var path = (VirtualPathUtility.GetDirectory(virtualPath) != "~/") ? VirtualPathUtility.RemoveTrailingSlash(VirtualPathUtility.GetDirectory(virtualPath)) : VirtualPathUtility.GetDirectory(virtualPath);
       if (path.Equals("~/Views/Routing", StringComparison.OrdinalIgnoreCase) || path.Equals("/Views/Routing", StringComparison.OrdinalIgnoreCase))
           return true;
       else
           return false;
   }
   

2. 现在，如果这个页面是从数据库提供的，它就是一个虚拟页面，那么接下来发生的事情就是它调用您的 MvcHandler(在我的处理程序中我有这些函数)

   protected override IAsyncResult BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, object state)
   {
       var vpp = new SkipstoneVirtualPathProvider(); // Create an instance of our VirtualPathProvider class
       var requestContext = ((MvcHandler)httpContext.Handler).RequestContext; // Get our request context
       var path = requestContext.HttpContext.Request.Url.AbsolutePath; // Get our requested path
       var pages = vpp.Pages; // Get all the published pages for this company
   
       if (pages != null && !string.IsNullOrEmpty(path)) // If we have any pages and we have a path
       {
           var page = this.MatchPage(pages, path);
           if (page != null) // If we find the page
           {
               requestContext.RouteData.Values["controller"] = "Routing"; // Set the controller
               requestContext.RouteData.Values["action"] = "Index"; // And the action
           }
       }
   
       return base.BeginProcessRequest(httpContext, callback, state);
   }
   
   private Page MatchPage(IList<Page> pages, string path)
   {
       if (path == "/" || !path.EndsWith("/"))
       {
           var page = pages.Where(model => model.Path.Equals(path, StringComparison.OrdinalIgnoreCase)).SingleOrDefault(); // Try to match the path first
           if (page == null) // If we have no page, then get the directory and see if that matches any page
           {
               path = VirtualPathUtility.RemoveTrailingSlash(VirtualPathUtility.GetDirectory(path));
               page = pages.Where(model => model.Path.Equals(path, StringComparison.OrdinalIgnoreCase)).SingleOrDefault();
           }
   
           return page; // return our page or null if no page exists
       }
   
       return null; // return null if anything fails
   }
   

3. 以防万一，如果您尚未创建 MvcHandler，则必须像这样在 RouteConfig 中注册它:

       // default MVC route
       routes.MapRoute(
           name: "Default",
           url: "{controller}/{action}/{id}",
           defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
       ).RouteHandler = new SkipstoneRouteHandler();
   

4. 在我的 MvcHandler 中，我获取我的页面，如果它与我移动到 RoutingController

   的任何虚拟页面匹配

   public ActionResult Index()
   {
       using (var uow = new UnitOfWork<SkipstoneContext>())
       {
           var userId = User.Identity.GetUserId();
           var service = new PageService(uow, this.CompanyId);
           var userService = new UserService(uow, this.CompanyId);
           var user = userService.Get(userId);
   
           var fileName = service.View(Request.Url, user);
   
           if (!fileName.StartsWith(@"/") && !fileName.StartsWith("~/"))
               return View(fileName); // Show the page
           else
               return Redirect(fileName); // Redirect to our page
       }
   }
   

为了您的方便，我将展示service.View 方法

    /// <summary>
    /// Views the CMS page
    /// </summary>
    /// <param name="uri">The current Request.Url</param>
    /// <param name="user">The current User</param>
    /// <returns>The filename of the requested page</returns>
    public string View(Uri uri, User user)
    {
        var path = uri.AbsolutePath; // Get our Requested Url
        var queryString = uri.Query;
        var pages = this.GetPublished();
        var page = pages.Where(model => model.Path.Equals(path, StringComparison.OrdinalIgnoreCase)).SingleOrDefault(); // Try to get the page

        if (page == null) // If our page is null
            page = pages.Where(model => model.Path.Equals(VirtualPathUtility.RemoveTrailingSlash(VirtualPathUtility.GetDirectory(path)))).SingleOrDefault(); // try to get the page based off the directory

        if (page == null) // If the page is still null, then it doesn't exist
            throw new HttpException(404, "This page has been deleted or removed."); // Throw the 404 error

        if (page.Restricted && user == null) // If our page is restricted and we are not logged in
            return "~/Account/LogOn?ReturnUrl=" + page.Path + queryString; // Redirect to the login page

        if (user != null && page.Restricted)
        {
            if (PageService.IsForbidden(page, user))
                throw new HttpException(401, "You do not have permission to view this page."); // Throw 401 error
        }

        return Path.GetFileNameWithoutExtension(page.Id.ToString());
    }

1. 然后我们被带回我们的 VirtualPathProvider 并且该过程再次开始，但是这次虚拟路径看起来像这样:"~/Views/Routing/1331.aspx"
2. 如果您注意到，我的 FindPage 方法还会查找我也存储在数据库中的扩展名匹配项:
3. 然后 GetFile 将被调用，只要您遵循我的路径，您应该返回 VirtualFile

我真的希望能有所帮助:)