Output Caching in ASP.NET MVC4

You can dramatically improve the performance of your ASP.NET MVC application very easily by taking advantage of the built-in output caching attributes. If you have an application that gets alot of traffic on a specific page , or returns a large list of records from a database you can use the output caching mechanism to cache the content returned by a controller action. And in doing so the same content does not need to be generated each and every time the same controller action is invoked causing unnecessary database hits and slowing down your page.

Most Output caching can be implemented very easily in MVC4 by using the standard OutputCacheAttribute class without having to go down the route of building a custom output cache provider. By decorating your controller actions with the outputcache attributes , you can maintain control over the duration of the cache of your actions.

First off , it's important to note that by default actions in asp.NET MVC have a cache-control of private.Which you can see by creating a simple action like the one below :

public JsonResult Details(int id)

{

////code here to get your results for your id

return Json(result, JsonRequestBehavior.AllowGet);

}


And then checking the header in the response in Fiddler or your tool of choice , and  you will see the cache-control :

Cache-Control:private

Connection:Close

Content-Length:81836

Content-Type:application/json; charset=utf-8

Date:Mon, 29 Oct 2012 08:08:44 GMT

Server:ASP.NET Development Server/11.0.0.0

X-AspNet-Version:4.0.30319

X-AspNetMvc-Version:3.0

This means that the browser might cache such ajax request made by a JavaScript client, which most of the time might not be desired. And can result in unexpected behaviour , especially in IE which is cache hungry. So often it is desirable to control what is cached and when yourself just to have some confidence in what is going on.

ASP.NET MVC Build-in caching mechanism

 You can control output caching by using the build-in output cache in asp.NET MVC. To do this you can decoration your controller actions with the outputcache attribute as follows.

[OutputCache(Duration = 6)]

public ActionResult Search(string searchText)

{

return Json(SearchWebService.MyWebServiceInstance.AutocompleteSearchClient(searchText),JsonRequestBehavior.AllowGet);

}

Now if we check our headers again , we can see our cache-control change :

Cache-Control: public, max-age=6

Expires: Mon, 29 Oct 2012 09:18:37 GMT

Last-Modified: Mon, 29 Oct 2012 09:18:34 GMT

Connection:Close

Content-Length:81836

Content-Type:application/json; charset=utf-8

Date:Mon, 29 Oct 2012 08:08:44 GMT

Server:ASP.NET Development Server/11.0.0.0

X-AspNet-Version:4.0.30319

X-AspNetMvc-Version:3.0

To see it in action for yourself , create a simple action like the one above , at first without the caching attribute and put a breakpoint in your controller action , you will note when you F5 the page , that it will hit the breakpoint every time.After decorating your action with the atttribute above , if you then run up your application , and F5 your page again , you can see that after the initial breakpoint being hit , the contents are cached and the breakpoint isnt hit again until your cache duration times out.

VaryByParam

The VaryByParam allows you to have different cached versions of the very same content. This property enables you to create different cached versions of the very same content for example when a query string parameter varies. By setting the VaryByParam property to “none” ,when the action is invoked, the same cached version of the action is returned i.e. any query string parameters are ignored , so usually if we have an action for a particular id , we'd want this to be cached based on the id , so we dont get the same results back.

If we have a number of params , and we want them all to be noted in the cache , we can either specific them semi-colon seperated list, or use the * in the VaryByParam value. E.G in the action which populates a grid below , we dont want the paging , sort and id queryparams to be ignored.

[OutputCache(Duration = 1, VaryByParam = "*")]

public ActionResult Index(int accountId, string page, string sort, string sortdir)

{

///code to get all accounts

return PartialView("_AccountsList", data);

}

File upload in MVC3/4

Those new to MVC or coming from classic ASP.NET might be a little daunted when first tasked with uploading a file in MVC , as there's no concept of the fileupload control (or any server side control for that matter)?

Thanks to Darin Dimitrov for the great example here:

Your controller

public class HomeController : Controller
{
// This action renders the form
public ActionResult Index()
{
return View();
}
// This action handles the form POST and the upload
[HttpPost]
public ActionResult Index(HttpPostedFileBase file)
{
// Verify that the user selected a file
if (file != null && file.ContentLength > 0)
{
// extract only the fielname
var fileName = Path.GetFileName(file.FileName);
// store the file inside ~/App_Data/uploads folder
var path = Path.Combine(Server.MapPath("~/App_Data/uploads"), fileName);
file.SaveAs(path);
}
// redirect back to the index action to show the form once again
return RedirectToAction("Index");
}
}

The view

@using (Html.BeginForm("Index", "Home", FormMethod.Post, new { enctype = "multipart/form-data" }))
{
<input type="file" name="file" />
<input type="submit" value="OK" />
}