How it works...

Let's take a quick look at what happened in the previous section. The interesting parts are steps 3 and 4.

In step 3, you installed the Nancy.Hosting.Aspnet package and the Nancy NuGet packages into the newly created HelloNancy project. This will download the Nancy assembly and the Nancy.Hosting.Aspnet assembly from the NuGet gallery, and add references to both in the HelloNancy project. The Nancy assembly is the Nancy framework, and the Nancy.Hosting.Aspnet assembly is an adapter for running the Nancy application on top of ASP.NET. In Nancy terms, this is called hosting Nancy on ASP.NET. Hosting is the subject of the Separating application and hosting (Advanced) recipe.

In step 4, you created a NancyModule class. Nancy modules are at the heart of Nancy applications. They are used to define which routes the application accepts and how it handles each one. For instance, the NancyModule class in step 4 defines one route and a handler for that route. This is done in the following line:

      Get["/"] = _ => "Hello Nancy World";

This tells Nancy that an HTTP GET request to the route "/" should be handled by the lambda expression on the right-hand side of the = sign. In other words, each time Nancy receives an HTTP GET "/", it calls the following line of code:

_ => "Hello Nancy World";

In the previous line of code, the lambda expression takes one parameter called _. It doesn't use the parameter for anything but simply returns the Hello Nancy World string back to Nancy. Since nothing went wrong, Nancy will create an HTTP 200 OK response with Hello Nancy World in the body and return it as the response to HTTP GET "/".

On a side note, I like to adopt the convention that whenever a parameter in a lambda is not used in the body of the lambda, I call it _. I like this because visually it makes the parameter almost disappear, so I instantly know that it is not used. On the other hand, if it is used, I will always give it a name. I will be using _ throughout this book for unused parameters.

On start-up, Nancy will find all Nancy modules in all loaded assemblies and instantiate each one. In the case of the module from step 4 in the previous section, the constructor containing the route definition discussed previously is run.