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Archive for the category “ASP.NET”

PerfMatters.Flush now CourtesyFlush

Pluralsight If you like my blog, you’ll love my Pluralsight courses:
Tracking Real World Web Performance
WebPageTest Deep Dive

Its been nearly a month since I released PerfMatters.Flush on NuGet. The library has been getting people talking about performance and thinking how to improve their web applications.

Unfortunately for me, I regretted releasing the library almost instantly, or at least as soon as Mike O’Brien suggested a much better name for it on Twitter:

For the uninitiated, a courtesy flush refers to the first, early flush you do in the restroom to avoid stinking the place up.


My library is basically the same thing, except, in a much more hygienic environment. Flushing your HTTP response early also provides everyone a benefit.

All that to say I’ve decided to rename PerfMatters.Flush to CourtesyFlush. I’ve “redirected” the old package to use the new one, so you don’t need to worry if you were using the old library. In addition, I’ve also added support for .NET 4.0 in this release.

PerfMatters.Flush Goes 1.0!

Pluralsight If you like my blog, you’ll love my Pluralsight courses:
Tracking Real World Web Performance
WebPageTest Deep Dive

In my previous two performance related posts I’ve gone on and on about the benefits of flushing an HTTP response early and how to do it in ASP.NET MVC. If you haven’t read those yet, I recommend you take a quick moment to at least read Flushing in ASP.NET MVC, and if you have a little extra time go through More Flushing in ASP.NET MVC as well.

I think those posts did a decent job of explaining why you’d want to flush early. In this post I’m going to dig into the details of how to flush early using my library, PerfMatters.Flush.

Three Usage Patterns

The core of what you need to know to use PerfMatters.Flush is that I’ve tried to make it easy to use by providing a few different usage models. Pick the one that works best in your scenario, and feel free to mix and match across your application.

1. Attribute Based

The easiest way to use PerfMatters.Flush is via the [FlushHead] action filter attribute, like this:

[FlushHead(Title = "Index")]
public ActionResult Index()
      // Do expensive work here
      return View();

The attribute can be used alone for HTML documents with a static <head> section. Optionally, a Title property can be set for specifying a dynamic <title> element, which is very common.

2. Code Based

For more complex scenarios, extension methods are provided which allow you to set ViewData or pass along a view model:

public ActionResult About()
     ViewBag.Title = "Dynamic title generated at " + DateTime.Now.ToLocalTime();
     ViewBag.Description = "A meta tag description";
     ViewBag.DnsPrefetchDomain = ConfigurationManager.AppSettings["cdnDomain"];


     // Do expensive work here
     ViewBag.Message = "Your application description page.";
     return View();

As you can see, this mechanism allows for very dynamic <head> sections. In this example you could imagine a <title> element, <meta name="description" content="…"> attribute (for SEO purposes) and <link rel="dns-prefetch" href="…"> (for performance optimization) all being set.

3. Global Lambda

Finally, PerfMatters.Flush offers a model to flush early across all your application’s action methods – which simply leverages the same global action filters that have been in ASP.NET MVC for years now:

public static void RegisterGlobalFilters(GlobalFilterCollection filters)
     filters.Add(new HandleErrorAttribute());
     filters.Add(new FlushHeadAttribute(actionDescriptor =>
         new ViewDataDictionary<CustomObject>(new CustomObject())
             {"Title", "Global"},
             {"Description", "This is the meta description."}

In this case we pass a Func<ActionDescriptor, ViewDataDictionary> to the FlushHeadAttribute constructor. That function is executed for each action method. This example is pretty contrite since the result is deterministic, but you can see both a custom model (CustomObject) and ViewData in use at the same time.

In real world usage the actionDescriptor parameter would be analyzed and leveraged to get data from some data store (hopefully in memory!) or from an IOC container.

Installation & Setup

Getting up and running with PerfMatters.Flush is as easy as installing the NuGet package.

From there, you’ll want to move everything you’d like to flush out of _Layout.cshtml to a new file called _Head.cshtml (which sits in the same directory). Here’s an example of _Head.cshtml:

<!DOCTYPE html>
     <meta charset="utf-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     @if (ViewBag.Description != null)
         <meta name="description" content="@ViewBag.Description">
     <title>@ViewBag.Title - My ASP.NET Application</title>

Here’s its corresponding _Layout.cshtml file:

     <!-- Lots of lovely HTML -->
     <div class="container body-content">
         <hr />
             <p>&copy; @DateTime.Now.Year - My Application</p>
     @RenderSection("scripts", required: false)

Notice the @Html.FlushHead() method on the first line? That’s the magic that stiches this all together. It allows you to use MVC the way your used to on action methods that you don’t want to flush early, and opt-in (via one of the usage model’s described above) when you do.

Wrapping Up

PerfMatters.Flush has been fun for me to work on. It’s currently being used in production on and has nicely boosted perceived performance on the pages that do any database queries.

To be honest, I wish that PerfMatters.Flush didn’t have to exist. I’ve asked the ASP.NET team to look into baking first class support for flushing early into the framework, but I don’t foresee that happening for quite awhile. Either way, there are tons of application built in MVC 3, 4 and 5 that can leverage this now.

The project is open source, and the code is hosted on GitHub. I’d love to hear your feedback on ways to make it better and easier to use.

New Job

“Choose a job you love, and you will never have to work a day in your life”.

It’s no secret that my love of web development has materialized into Glimpse, the project I started a little over a year ago with Anthony Van der Hoorn. I’ve had an amazing ride with Glimpse; becoming an ASP Insider, getting to meet many of my dev heroes and working with fantastic contributors from all around the world.

About a month ago that ride took a new and unexpected turn. An opportunity to work full time with the open source community on our little project arose from a seemingly unexpected source: Red Gate.

Red Gate

I was taken surprised by Red Gate’s proposal and spent several weeks with Anthony and Red Gate’s top brass discussing our philosophies of open development, open source, ASP.NET, the web development community, software development practices and yes, even Reflector. As the discussions progressed I became more and more convinced that Red Gate genuinely believed in our vision of Glimpse, our model of development, and most importantly, the community that we were serving. Given that, I decided to take a new job with Red Gate – getting to focus a much larger portion of my time on the things I love: Glimpse and the web development community.

There are a lot more details about what this means for Glimpse on the Glimpse blog, so I won’t rehash that here, but in summary it’s all positive. From a personal perspective, I will remain in New York City, and, in addition to spending a majority of my time working on Glimpse, I have also been given the opportunity to interact with the community. This basically means that part of my new position requires writing blog posts, speaking at user groups/meetups, working with open source and attending conferences like Monospace in October.

This is all new and very exciting to me. Keep an eye on this blog and my twitter feed for updates as things progress.

– By


JSON with Padding (JSONP) is a slight “hack” to allow for cross origin ajax requests. Instead of making requests the standard ajax way, leveraging XMLHttpRequest, JSONP techniques make requests by writing a <script> tag into the DOM with the src attribute set to the appropriate URL. Because browsers do not limit the origin of scripts loaded via the <script> tag, data, via JavaScript, can be loaded from any of the hundreds of API’s and endpoints that support JSONP.

Consuming JSONP services is ridiculously easy and has had support built into jQuery since version 1.2.

$(function () {
        dataType: 'jsonp',
        url: '',
        success: function (data) {

In this case, the data that is returned from the server is logged to the browser console, but any JavaScript could be executed.

Enabling JSONP on top of an existing JSON endpoint (server side) is fairly simple. It requires changing the HTTP response content type, and wrapping the resultant JSON string in a JavaScript function call (the padding part).

Unfortunately, ASP.NET MVC does not ship with JSONP support out of the box, but it is easy to add with the great extensibility points available in MVC. Here is an implementation of an MVC ActionResult which would enable any controller to begin to return proper JSONP results.

using System;
using System.Text;
using System.Web;
using System.Web.Mvc;
using System.Web.Script.Serialization;

namespace NikCodes.ActionResults
    public class JsonpResult : ActionResult
        public string CallbackFunction { get; set; }
        public Encoding ContentEncoding { get; set; }
        public string ContentType { get; set; }
        public object Data { get; set; }

        public JsonpResult(object data):this(data, null){}
        public JsonpResult(object data, string callbackFunction)
            Data = data;
            CallbackFunction = callbackFunction;

        public override void ExecuteResult(ControllerContext context)
            if (context == null) throw new ArgumentNullException("context");

            HttpResponseBase response = context.HttpContext.Response;

            response.ContentType = string.IsNullOrEmpty(ContentType) ? "application/x-javascript" : ContentType;

            if (ContentEncoding != null) response.ContentEncoding = ContentEncoding;

            if (Data != null)
                HttpRequestBase request = context.HttpContext.Request;

                var callback = CallbackFunction ?? request.Params["callback"] ?? "callback";

#pragma warning disable 0618 // JavaScriptSerializer is no longer obsolete
                var serializer = new JavaScriptSerializer();
                response.Write(string.Format("{0}({1});", callback, serializer.Serialize(Data)));
#pragma warning restore 0618

This action result simply takes in an object, serializes it using the standard MVC serialization method and wraps it up in a callback function. It supports jQuery’s JSONP implementation transparently. Using it couldn’t be simpler:

public ActionResult ActionMethod()
    var data = GetDataSomehow();
    return new JsonpResult(data);
    //constructor overload for overriding callback function
    //return new JsonpResult(data, "callback function"); 

Of course, cross origin resource sharing (CORS) is much more powerful that JSONP, and will ultimately replace it – but until then, or as long as we have < IE 10, we will still have to leverage this technique.

Download the code, try it out. Let me know if this is valuable enough to put on NuGet.

– By

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