Views in separate assemblies in ASP.NET MVC

It took me way too long to get this working properly from the various partial samples, so here’s the full code needed to get views from a Views folder in a shared library structured the same as a regular Views folder but with everything set to build as embedded resources. It will only use the embedded file if the usual file does not exist.

The first line of Application_Start:

HostingEnvironment.RegisterVirtualPathProvider(new EmbeddedViewPathProvider());

The VirtualPathProvider

   public class EmbeddedVirtualFile : VirtualFile
{
    public EmbeddedVirtualFile(string virtualPath)
        : base(virtualPath)
    {
    }

    internal static string GetResourceName(string virtualPath)
    {
        if (!virtualPath.Contains("/Views/"))
        {
            return null;
        }



        var resourcename = virtualPath
            .Substring(virtualPath.IndexOf("Views/"))
            .Replace("Views/", "OrangeGuava.Common.Views.")
            .Replace("https://stackoverflow.com/", ".");

        return resourcename;

    }


    public override Stream Open()
    {
        Assembly assembly = Assembly.GetExecutingAssembly();


        var resourcename = GetResourceName(this.VirtualPath);
        return assembly.GetManifestResourceStream(resourcename);
    }




}

public class EmbeddedViewPathProvider : VirtualPathProvider
{


    private bool ResourceFileExists(string virtualPath)
    {

        Assembly assembly = Assembly.GetExecutingAssembly();


        var resourcename = EmbeddedVirtualFile.GetResourceName(virtualPath);
        var result = resourcename != null && assembly.GetManifestResourceNames().Contains(resourcename);
        return result;
    }

    public override bool FileExists(string virtualPath)
    {
        return base.FileExists(virtualPath) || ResourceFileExists(virtualPath);
    }


    public override VirtualFile GetFile(string virtualPath)
    {

        if (!base.FileExists(virtualPath))
        {
            return new EmbeddedVirtualFile(virtualPath);
        }
        else
        {
            return base.GetFile(virtualPath);
        }

    }

}

The final step to get it working is that the root Web.Config must contain the right settings to parse strongly typed MVC views, as the one in the views folder won’t be used:

<pages
    validateRequest="false"
    pageParserFilterType="System.Web.Mvc.ViewTypeParserFilter, System.Web.Mvc, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"
    pageBaseType="System.Web.Mvc.ViewPage, System.Web.Mvc, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"
    userControlBaseType="System.Web.Mvc.ViewUserControl, System.Web.Mvc, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35">
  <controls>
    <add assembly="System.Web.Mvc, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" namespace="System.Web.Mvc" tagPrefix="mvc" />
  </controls>
</pages>

A couple of additional steps are required to get it working with Mono. First, you need to implement GetDirectory, since all files in the views folder get loaded when the app starts rather than as needed:

public override VirtualDirectory GetDirectory(string virtualDir)
    {
        Log.LogInfo("GetDirectory - " + virtualDir);
        var b = base.GetDirectory(virtualDir);
        return new EmbeddedVirtualDirectory(virtualDir, b);
    }

public class EmbeddedVirtualDirectory : VirtualDirectory
{
    private VirtualDirectory FileDir { get; set; } 

    public EmbeddedVirtualDirectory(string virtualPath, VirtualDirectory filedir)
        : base(virtualPath)
    {
        FileDir = filedir;
    }

    public override System.Collections.IEnumerable Children
    {
        get { return FileDir.Children; }
    }

    public override System.Collections.IEnumerable Directories
    {
        get { return FileDir.Directories; }
    }

    public override System.Collections.IEnumerable Files
    {
        get {

            if (!VirtualPath.Contains("/Views/") || VirtualPath.EndsWith("/Views/"))
            {
                return FileDir.Files;
            }

            var fl = new List<VirtualFile>();

            foreach (VirtualFile f in FileDir.Files)
            {
                fl.Add(f);
            }


            var resourcename = VirtualPath.Substring(VirtualPath.IndexOf("Views/"))
.Replace("Views/", "OrangeGuava.Common.Views.")
.Replace("https://stackoverflow.com/", ".");

            Assembly assembly = Assembly.GetExecutingAssembly();

            var rfl = assembly.GetManifestResourceNames()
                .Where(s => s.StartsWith(resourcename))
                .Select(s => VirtualPath + s.Replace(resourcename, ""))
                .Select(s => new EmbeddedVirtualFile(s));
            fl.AddRange(rfl);

            return fl;
        }
    }
}

Finally, strongly typed views will almost but not quite work perfectly. Model will be treated as an untyped object, so to get strong typing back you need to start your shared views with something like

<% var Model2 = Model as IEnumerable<AppModel>;  %>