VirtualPathProvider in MVC 5 - asp.net-mvc

Question

I can't seem to get a custom VirtualPathProvider working in asp.net MVC 5.
The FileExists method returns true but then the GetFile method isn't called.
I believe this is because IIS takes over the request and does not let .NET handle it.
I have tried setting RAMMFAR and creating a custom handler, as in this solution https://stackoverflow.com/a/12151501/801189 but still no luck. I get a error 404.
My Custom Provider:
public class DbPathProvider : VirtualPathProvider
{
public DbPathProvider() : base()
{
}
private static bool IsContentPath(string virtualPath)
{
var checkPath = VirtualPathUtility.ToAppRelative(virtualPath);
return checkPath.StartsWith("~/CMS/", StringComparison.InvariantCultureIgnoreCase);
}
public override bool FileExists(string virtualPath)
{
return IsContentPath(virtualPath) || base.FileExists(virtualPath);
}
public override VirtualFile GetFile(string virtualPath)
{
return IsContentPath(virtualPath) ? new DbVirtualFile(virtualPath) : base.GetFile(virtualPath);
}
public override CacheDependency GetCacheDependency(string virtualPath, IEnumerable virtualPathDependencies, DateTime utcStart)
{
return null;
}
public override String GetFileHash(String virtualPath, IEnumerable virtualPathDependencies)
{
return Guid.NewGuid().ToString();
}
}
My Custom Virtual File:
public class DbVirtualFile : VirtualFile
{
public DbVirtualFile(string path): base(path)
{
}
public override System.IO.Stream Open()
{
string testPage = "This is a test!";
return new System.IO.MemoryStream(System.Text.ASCIIEncoding.ASCII.GetBytes(testPage));
}
}
web.config handler I have tried to use, without success. It currently gives error 500 :
<system.webServer>
<modules runAllManagedModulesForAllRequests="true">
<remove name="FormsAuthenticationModule" />
</modules>
<handlers>
<add name="ApiURIs-ISAPI-Integrated-4.0"
path="/CMS/*"
verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS"
type="System.Web.Handlers.TransferRequestHandler"
preCondition="runtimeVersionv4.0" />
</handlers>
If I try to navigate to site.com/CMS/Home/Index, the FileExists method is called but strangely, the virtualPath parameter recieves only ~/CMS/Home.
Adding breakpoints, it seems that for the url site.com/CMS/Home/Index, the FileExists method keeps getting repeatedly called. This may be causing an infinite recursion, giving the internal server error.

Answer 1

It was actually nothing to do with IIS, and in fact confusion on the order of events. It seems I didn't understand that a routed action method must return a view, that the VirtualPathProvider will try to resolve, rather than going to the VirtualPathProvider directly.
I create a simple controller called ContentPagesController with a single GetPage action:
public class ContentPagesController : Controller
{
[HttpGet]
public ActionResult GetPage(string pageName)
{
return View(pageName);
}
}
I then set up my route to serve virtual pages:
routes.MapRoute(
name: "ContentPageRoute",
url: "CMS/{*pageName}",
defaults: new { controller = "ContentPages", action = "GetPage" },
constraints: new { controller = "ContentPages", action = "GetPage" }
);
I register my custom VirtualPathProvider before I register my routes, in globals.asax.cs.
Now suppose I have a page in my database with the relative url /CMS/Home/AboutUs. The pageName parameter will have value Home/AboutUs and the return View() call will instruct the VirtualPathProvider to look for variations of the file ~/Views/ContentPages/Home/AboutUs.cshtml.
A few of the variations it will be look for include:
~/Views/ContentPages/Home/AboutUs.aspx
~/Views/ContentPages/Home/AboutUs.ascx
~/Views/ContentPages/Home/AboutUs.vbhtml
All you now need to do is check the virtualPath that is passed to the GetFiles method, using a database lookup or similar. Here is a simple way:
private bool IsCMSPath(string virtualPath)
{
return virtualPath == "/Views/ContentPages/Home/AboutUs.cshtml" ||
virtualPath == "~/Views/ContentPages/Home/AboutUs.cshtml";
}
public override bool FileExists(string virtualPath)
{
return IsCMSPath(virtualPath) || base.FileExists(virtualPath);
}
public override VirtualFile GetFile(string virtualPath)
{
if (IsCMSPath(virtualPath))
{
return new DbVirtualFile(virtualPath);
}
return base.GetFile(virtualPath);
}
The custom virtual file will be made and returned to the browser in the GetFile method.
Finally, a custom view engine can be created to give different virtual view paths that are sent to VirtualPathProvider.
Hope this helps.