Custom Virtual Path Provider in IIS

What is the correct configuration to implement a custom virtual path provider in IIS 7.5? The following code works as expected when run from Visual Studio using the ASP.NET Development Server but does not load the image when run from IIS.

.NET 4.0 Project File

CustomVirtualPathProvider.zip - SkyDrive file

Web.config

<?xml version="1.0"?>
<configuration>
  <system.web>
    <compilation debug="true" targetFramework="4.0" />
  </system.web>
  <system.webServer>
     <modules runAllManagedModulesForAllRequests="true"/>
  </system.webServer>
</configuration>

Default.aspx

<%@ Page Title="Home Page" Language="C#" AutoEventWireup="true" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
    <head>
        <title>Virtual Path Provider</title>
    </head>
    <body>
        <img src="Box.png" />
    </body>
</html>

Global.asax

public class Global : System.Web.HttpApplication
{
    void Application_Start(object sender, EventArgs e)
    {
        System.Web.Hosting.HostingEnvironment.RegisterVirtualPathProvider(new WebApplication1.CustomVirtualPathProvider());
    }
}

CustomVirtualFile.cs

public class CustomVirtualFile : System.Web.Hosting.VirtualFile
{
    private string _VirtualPath;

    public CustomVirtualFile(string virtualPath) : base(virtualPath)
    {
        _VirtualPath = virtualPath.Replace("/", string.Empty);
    }

    public override Stream Open()
    {
        string ImageFile =
            System.IO.Path.Combine(HttpContext.Current.Request.PhysicalApplicationPath, @"Crazy\Image\Path", _VirtualPath);
        return System.IO.File.Open(ImageFile, FileMode.Open, FileAccess.Read);
    }
}

CustomVirtualPathProvider.cs

public class CustomVirtualPathProvider : System.Web.Hosting.VirtualPathProvider
{
    Collection<string> ImageTypes;

    public CustomVirtualPathProvider() : base()
    {
        ImageTypes = new Collection<string>();
        ImageTypes.Add(".PNG");
        ImageTypes.Add(".GIF");
    }

    public override bool FileExists(string virtualPath)
    {
        if (IsImage(virtualPath))
        {
            return true;
        }
        return base.FileExists(virtualPath);
    }

    public override System.Web.Hosting.VirtualFile GetFile(string virtualPath)
    {
        if (IsImage(virtualPath))
        {
            return new CustomVirtualFile(virtualPath);
        }
        return base.GetFile(virtualPath);
    }

    private bool IsImage(string file)
    {
        return ImageTypes.IndexOf(file.ToUpperInvariant().Substring(file.Length - 4, 4)) > -1;
    }
}

Filesystem

\Crazy\Image\Path\Box.png

IIS Configuration

Default site with no configuration changes.

Adam Carr

Here is what I found to "fix" my issue.

http://sunali.com/2008/01/09/virtualpathprovider-in-precompiled-web-sites/

In brief:

HostingEnviornment explicitly ignores Virtual Path Providers in precompiled sites. You can circumvent this limitation by using reflection to call an internal version that omits this check. Thus, instead of calling

HostingEnviornment.RegisterVirtualPathProvider(new EmbeddedViewVirtualPathProvider();

call this instead:

typeof(HostingEnvironment).GetMethod("RegisterVirtualPathProviderInternal",
      BindingFlags.Static | BindingFlags.InvokeMethod | BindingFlags.NonPublic)
    .Invoke(null, new object[] {new EmbeddedViewPathProvider()});

I had the same problem but Tom Clarkson led me on the right track, he's absolutely right in that you need additional configuration in order to make IIS serve the content provider by the virtual path provider. I found a solution here

Here is an example web.config-snippet that I think will work for you

<system.web>
  <httpHandlers>
    <add path="*.png" verb="*" type="System.Web.StaticFileHandler" validate="true" />
    <add path="*.gif" verb="*" type="System.Web.StaticFileHandler" validate="true" />
  </httpHandlers>
</system.web>

You could also register a "wildcard httphandler" under a special location (eg "/MyVirtualFiles"), which might be useful if your virtual path provider serves many different file types.

<location path="MyVirtualFiles">
  <system.web>
    <httpHandlers>
      <add path="*" verb="*" type="System.Web.StaticFileHandler" validate="true" />
    </httpHandlers>
  </system.web>
</location>

When FileExists returns true, it is interpreted as "there is a file there, IIS can serve it without ASP.NET". To get the next step of actually downloading the file to go through your virtual path provider, you need to set IIS to use ASP.NET to serve all image files and add code in global.asax or an http handler that will make use of your virtual path provider.

来源：https://stackoverflow.com/questions/4235337/custom-virtual-path-provider-in-iis

标签

ASP.NET

iis-7.5