Why use Nancy?

NancyFXOn one of my posts showing how you can use Nancy with ASP.NET Core, David Anderson posted the following comment

I came across some Nancy blogpost last week and got curious about it and so looked on internet for more information. I wanted to know why should someone use Nancy and why plain asp.net core is not sufficient. So far every place I look I see the same introduction, you know that one with ‘…super-duper-happy-path…’. But to be honest it’s still not clear ‘why’? What is it that someone can not do in ASP.NET Core which is ‘super-duper’ in Nancy? What is hard or missing in ASP.NET Core which is easy or available in Nancy? The need of such a framework on top of ASP.NET Core is very vage to me.

I realized that I never really blogged about why I started using Nancy.  I hinted at it slightly in my post about ASP.NET Core MVC Attribute Routing, but not in much detail.

MVC & Web API Routing

Like most, I primarily used ASP.NET MVC and Web API.  When I got into creating more Web API’s, the first thing that started causing me trouble was routing.

The convention based routing employed is to define your routes in the RouteCollection.  This is the familiar default route that you might have used before.

The primary issue I had with defining routes and route templates up front, was I to defined them closer to the code that was actually executing at a given endpoint.

Route Attributes do ultimately solve this problem and from what I’ve read recently, this seems to be the common way most now define routes.  However, I’m simply not a fan of attributes in this situation.  I won’t get into the reasons why, as I don’t think starting an attribute war serves much purpose for this post.

Nancy Routes

When I first seen how you defined routes in Nancy, I realized it was exactly what I was looking for.

Routes are defined in the constructor of a module. In order to define a route in Nancy, you need to specify a Method + Pattern + Action + (optional) Condition.

They’re just endpoints…

When you look at a Nancy module, you could compare it to a MVC or Web API Controller, but it’s really nothing more than a place you can define HTTP Endpoints.

This means you can use Modules as Controllers and develop using your familiar MVC pattern, or you could use them as Web API’s.  You can have your endpoint do whatever you need and return whatever you want.


Nancy by default is really simple to use.  You need zero configuration to get started.  Zero.

Add a Nancy Module and you are off to the races.

I’ve made a couple different posts on how you can use Nancy along side Web API in ASP.NET 4, and how you can use it with ASP.NET Core.


Back to the comment and the last sentence:

The need of such a framework on top of ASP.NET Core is very vage to me

Nancy doesn’t replaces ASP.NET Core, but it could replace your need for ASP.NET Core MVC.

With the application pipeline (middleware) in ASP.NET Core, this allows you to leverage many different components that serve different purposes all within your web application.

For example you could use Nancy, ASP.NET Core MVC, Static File Server and Authentication.

More Reasons

There are many more reasons and many considerations. I highly recommend reading a post by Jonathan Channon that covers different aspects.  The post that’s a tad old, but still very relevant.

I really enjoy the conversation I get in some of the comments.  Please leave a comment here or on twitter.

ASP.NET Core MVC Attribute Routing

Over the last several years, I haven’t done much work with ASP.NET 4 MVC.  I primarily have used ASP.NET Web API and then eventually went full on with Nancy.

My main reason for switching to Nancy for creating Web API’s was I wasn’t overly fond of the ASP.NET MVC/WebAPI Routing.   I really liked how you you defined routes in Nancy by specifying the route in the constructor of your Module/Controller which was close to the Action.

I tweeted this yesterday, and it seems I’m not alone.


I can’t say I’m a fan of attributes, that’s another blog post entirely, so I wont get into here.  But based on my current understanding of ASP.NET Core MVC, you can use Route attributes closer to the action.  So for my own experimenting, let’s give this a try and see how well it can work.

If you have any questions, please follow me on Twitter.


For reference, I’m using the ASP.NET Core Web API Template that comes with Visual Studio 2015.  All the source code for this blog post is on GitHub.

If we look at the ValuesController, it defines the base route as being “api/[controller]”.

If we translate this, we can make an HTTP call to  http://localhost:5000/api/values which should call the Get() method returning an string array.


Custom Action

Now let’s say I want to create a new method and define it a specific route “api/values/getmore” which should call the GetMoreStuff() method.

My first beginner thought was to specify a Route attribute on the action/method.


As you can see, it’s actually calling the Get(int) method and returning “value” rather than calling GetMoreStuff().

This is because the route attribute on the Get(int) HttpGet attribute is defining the route that is taking over.  Let’s change this a bit since I know know that the  HttpGet attributes first argument is the route template.


Huzzah! The results we expected.  However I’m not in love with the controller having the Route attribute to define the prefix to our route.  Let’s get rid of it and define routes per action/method.


Closer to the Action

This definitely puts our routes closer to the action, however I’m still not in love with attributes.

Let me know if you have any other options for defining routes closer to the action, but more specifically, in code.

If you have any questions, please follow me on Twitter.