Creating a custom ASP.NET Core Output Formatter

ASP.NET Core Output FormatterIf you follow my blog, you may also know that I’ve blogged a bit about Hypermedia.  Because I’m a fan, I’ve decided to start creating an custom ASP.NET Core Output Formatter to handle the Siren hypermedia specification (application/vnd.siren+json).

All the code samples in this blog post are pulled from a sample application of the game Hangman.   I’m creating it in ASP.NET Core.  I will eventually pull out the Output Formatter and create a repo on GitHub and a Nuget.

Output Formatter

Since I’m handling Text, I’m going to be deriving from the TextOutputFormatter.  This requires you to implement two methods:

bool CanWriteType(Type type)

This method determines if your output formatter can handle the type returned from your controller action.

Task WriteResponseBodyAsync(OutputFormatterWriteContext context, Encoding selectedEncoding)

Handle how yo want to transform the object returned from your controller action.

Lastly, you also need to define which media types your output formatter will handle.  In other words, when the client sends an Accept: header, which values apply to your output formatter.

In my case, Siren uses application/vnd.siren+json

MVC Options

Finally, in our startup, we need to add our new Output Formatter in the AddMVC extension method.


Here are two different outputs.  The first is with an Accept: application/json and the second is requestion Siren with Accept: application/vnd.siren+json

Stay Tuned

If you’re interested in supporting Siren in your ASP.NET Core MVC applications, I plan on publishing my small library soon to GitHub as well as Nuget.

Have you created a custom output formatter? I’d love to hear what your creating!  Let me know on Twitter or in the comments.

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LiteDB: Embedded .NET NoSQL Database

I was recently in the need for a simple NoSQL database that I could use for an app I was creating for a ASP.NET Core Workshop.

What I was really after was something similar to SQLite.   A single package I could pull into my application that did not require any external service and data stored in a single file.

It didn’t take long to find LiteDB.  After using it for my demo application, I had write a quick post about it.  Just to shed some light for anyone in need.  The project is actually really popular on GitHub, so it seems I might just be late to the party about finding out about it.


LiteDB is serverless database delivered in a single DLL (less than 350kb) fully written in .NET C# managed code (compatible with .NET 3.5, 4.x, NETStandard 1.3 and 2.0).

Install via NuGet or just copy DLL to your bin project folder.


Similar to MongoDB

One thing to note is how the API is similar to the Mongo DB .NET driver.

You also can store files like you can in GridFS.

Use Cases

I would think the use cases would be similar in terms of need for something like SQLite.  Because it supports .NET Standard, I would think Xamarin apps would be an excellent fit.

Again, my application was a small local application, which was also ideal.

Are you using LiteDB? Using something different? I’d love to hear what your using and your workloads which you’re using it in.  Let me know on Twitter or in the comments.

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.NET Video Tutorials

I’ve started a YouTube channel last year to provide some video content to many of my blog posts.  I’ve never really mentioned it on this blog, which seems crazy.  Primarily these are .NET Video Tutorials as well as recorded talks that I’ve done at various conferences.

Please take a look and subscribe if this is up your alley.  I plan on providing regular content on YouTube as well as continuing to do so on this blog.  Video just seems like a natural extension to provide content that is generally on this blog.

Popular Videos

How to Self Host ASP.NET Web API

Not everyone is able to migrate their applications to ASP.NET Core.  Many are not even aware that you can self-host a WebAPI project with Katana (Owin).  You can, here’s how!

Fat Controller CQRS Diet Series

My series of blog posts have backing tutorials to view.  As well as a talk around the overall concept.

Everyone Love Cake!

One of the first videos I’ve made was getting started with Cake for automating your build process.


I’m always looking for suggestions.  If you have any questions or suggestions for video tutorials or blog posts please let me know on Twitter or in the comments.  Over the years I’ve gotten some create feedback and it’s very appreciated.

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