Rendering a Razor view as a string within a Task - asp.net-mvc

Question

The following code works fine for rendering a Razor View to a string:
///
/// url: /api/createHtml
///
public ActionResult CreateHtml()
{
// Heavy calculations
MyModel myModel = new MyModel();
myModel.Feature1 = ...;
myModel.Feature2 = ...;
myModel.Feature3 = ...;
ViewData.Model = myModel;
using (var stringWriter = new StringWriter())
{
var viewResult = ViewEngines.Engines.FindPartialView(ControllerContext, "MyView");
var viewContext = new ViewContext(ControllerContext, viewResult.View, ViewData, TempData, stringWriter);
viewResult.View.Render(viewContext, stringWriter);
viewResult.ViewEngine.ReleaseView(ControllerContext, viewResult.View);
string html = stringWriter.GetStringBuilder().ToString();
byte[] htmlBytes = Encoding.ASCII.GetBytes(html);
System.IO.File.WriteAllBytes(Server.MapPath("~/temp/foo.html"), htmlBytes);
}
return JSON(new
{
error = false,
message = "Your view is available at temp/foo.html"
});
}
The above code runs synchronously, meaning that an AJAX request to /api/createHtml/ will finish with the temp/foo.html file created.
I want to do this asynchronously: meaning that the AJAX request returns fast to the user with a message like: "Your view WILL BE available at temp/foo.html". And then the user must go check if the file is ready (by simply polling to the temp directory [or using other method, not important in this question])
So, when I try the same code within a Task, it doesn't work:
///
/// url: /api/createHtml
///
public ActionResult CreateHtml()
{
new Task(() =>
{
// Heavy calculations
MyModel myModel = new MyModel();
myModel.Feature1 = ...;
myModel.Feature2 = ...;
myModel.Feature3 = ...;
ViewData.Model = myModel;
using (var stringWriter = new StringWriter())
{
var viewResult = ViewEngines.Engines.FindPartialView(ControllerContext, "MyView");
var viewContext = new ViewContext(ControllerContext, viewResult.View, ViewData, TempData, stringWriter);
viewResult.View.Render(viewContext, stringWriter); // <--- Problem
viewResult.ViewEngine.ReleaseView(ControllerContext, viewResult.View);
string html = stringWriter.GetStringBuilder().ToString();
byte[] htmlBytes = Encoding.ASCII.GetBytes(html);
System.IO.File.WriteAllBytes(Server.MapPath("~/temp/foo.html"), htmlBytes);
}
}).Start();
return JSON(new
{
error = false,
message = "Your view _WILL BE_ available at temp/foo.html"
});
}
It doesn't work because it throws an Exception at viewResult.View.Render(...)
Value does not fall within the expected range.
It seems that the viewContext passed to viewResult.View.Render(...) is no longer valid in the new thread, as shown here: ASP.NET MVC: Exception rendering view in new thread
Is there a workaround for rendering a view within a Task ?
I know I could use "RazorEngine", a free library that renders razor views without all the controller mumbo jumbo, but I'd prefer to use native code, for reutilization of the code.
POST EDITED:
The few answers thought that I wanted to use "await async". I don't. I don't want to wait for the task to finish.

Answer 1

Well your tasks is probably doing what it suppose to do, but the main threat is not waiting for him.
Try using:
var myTask=new Task(() =>
{
// all of your code
}).Start();
myTask.Wait();
check more info
The best way is using async and await, because Tasks should be used for asynchronous operations, good luck.

Answer 2

Asynchronous action methods, works async only inside the web server. The advantage of async methods is that they release the precious thread back to the thread pool, when they don't need it (as opposed to blocking it)... But the HttpRequest is still synchronous... your browser would synchronously wait for a response from an async action method.
What you need is to spawn a new thread or task to do your long running task and return from the action method.
Take a look at: Long Running Background Tasks in Asp.Net MVC3
Also this question might help: Do asynchronous operations in ASP.NET MVC use a thread from ThreadPool on .NET 4