Preload ASP.NET MVC views in IIS warmup step

Question

I recently began playing around with the ability of IIS to apply a warmup step step to my web application through use of the IProcessHostPreloadClient interface (look here for for guidance on how to set this up). This worked out great, or at least I thought it did, because one of the 'clever' things I did was to try and preload my views by iterating over my controllers and rendering them.

After a bit of trial and error, I got it to work and all was well. That is, until I noticed that all validation for my system no longer worked, neither client nor server validation. I assume that the validation is normally hooked up to the views when MVC retrieves a view for the first time and I failed to do so. Does anyone have an idea how this could be included in my solution or perhaps done in another way?

The code:

public class Warmup : IProcessHostPreloadClient
{
    public void Preload(string[] parameters)
    {
        //Pre-render all views
        AutoPrimeViewCache("QASW.Web.Mvc.Controllers", @"Views\");
        AutoPrimeViewCache("QASW.Web.Mvc.Areas.Api.Controllers", @"Areas\Api\Views\", "Api");
    }

    private void AutoPrimeViewCache(string controllerNamespace, string relativeViewPath, string area = null)
    {
        var controllerTypes = typeof(Warmup).Assembly.GetTypes().Where(t => t.Namespace == controllerNamespace && (t == typeof(Controller) || t.IsSubclassOf(typeof(Controller))));
        var controllers = controllerTypes.Select(t => new { Instance = (Controller)Activator.CreateInstance(t), Name = t.Name.Remove("Controller") });

        foreach (var controller in controllers)
        {
            var viewPath = Path.Combine(HostingEnvironment.ApplicationPhysicalPath, relativeViewPath + controller.Name);
            var viewDir = new DirectoryInfo(viewPath);
            if (viewDir.Exists)
            {
                var viewNames = viewDir.EnumerateFiles("*.cshtml").Select(f => f.Name.Remove(".cshtml")).ToArray();
                PreloadController(controller.Instance, area, viewNames);
            }
        }
    }

    private void PreloadController(Controller controller, string area, params string[] views)
    {
        var viewEngine = new RazorViewEngine();

        var controllerName = controller.GetType().Name.Remove("Controller");
        var http = new HttpContextWrapper(new HttpContext(new HttpRequest(null, "http://a.b.com", null), new HttpResponse(TextWriter.Null)));
        var routeDescription = area == null ? "{controller}/{action}/{id}" : area + "/{controller}/{action}/{id}";
        var route = new RouteCollection().MapRoute(
            "Default", // Route name
            routeDescription, // URL with parameters
            new { controller = "Home", action = "Index", id = UrlParameter.Optional }
        );

        var routeData = new RouteData(route, route.RouteHandler);
        routeData.Values.Add("controller", controllerName);
        if (area != null)
        {
            routeData.Values.Add("area", area);
            routeData.DataTokens.Add("area", area);
        }
        routeData.DataTokens.Add("controller", controllerName);
        routeData.Values.Add("id", 1);
        routeData.DataTokens.Add("id", 1);
        var controllerContext = new ControllerContext(http, routeData, controller);
        var vDic = new ViewDataDictionary();
        var vTemp = new TempDataDictionary();

        foreach (var view in views)
        {
            var viewResult = viewEngine.FindView(controllerContext, view, null, false);
            if (viewResult.View == null)
                throw new ArgumentException("View not found: {0} (Controller: {1})".Args(view, controllerName));
            var viewContext = new ViewContext(controllerContext, viewResult.View, vDic, vTemp, TextWriter.Null);
            try { viewResult.View.Render(viewContext, TextWriter.Null); }
            catch { }
        }
    }
}

Answer 1

Not direct answer to your question, but I think you should take a look at Precompiling MVC Razor views using RazorGenerator by David Ebbo

One reason to do this is to avoid any runtime hit when your site starts, since there is nothing left to compile at runtime. This can be significant in sites with many views.