Sitelets is an F#-based library, that provides abstractions for creating ASP.NET Core web applications.

• Installing
• Using Sitelets
• Working with other ANC web frameworks
• Contributing

The easiest way to add Sitelets to your project is by using dotnet cli:

dotnet add YOUR_PROJECTFILE package Sitelets

or if you work in Visual Studio, search for Sitelets in Nuget and install it in your project!

For example let's create an ASP.NET Core Mvc app and plug Sitelets into it to make a Hello World site:

dotnet new mvc -lang f# -o MyMvcApp

dotnet add MyMvcApp/MyMvcApp.fsproj package Sitelets

For clarity, let's add a MySitelets folder in to project and create a HelloWorld.fs source file in it. Now for this site we only want to print the 'Hello World' text onto the page, only this much code will do the job:

module Hello

    open Sitelets

    type EndPoint =
    | HelloEndPoint

    let helloWorldSite = Sitelet.Content "/hello" EndPoint.HelloEndPoint (fun _ -> box "Hello World")

We also have to plug the sitelet into the application pipeline. Go to Startup.fs and do this:

...

app.UseAuthorization() |> ignore

// plug sitelet in here for example
app.UseSitelets(Hello.helloWorldSite) |> ignore

app.UseEndpoints(fun endpoints ->
...

After a quick build and run, if you go to the /hello endpoint, you will see "Hello World" in the response. Now this example only shows how easy it is to grab the package and use it in project. Here's a glimpse of what makes Sitelets a powerful tool:

type Pizza =
    {
        Customer: string
        Size: int
    }

type EndPoint =
    | [<Method "GET"; EndPoint "/index">] Home
    | [<Method "GET"; EndPoint "/greet"; Query "firstname"; Query "lastname">] GreetPerson of firstname:string * lastname: string
    | [<Method "POST"; EndPoint "/order">; Json "pizza"] Order of pizza:Pizza

let inferSitelet =
    Sitelet.Infer (fun ctx -> function
        | Home -> // some content
        | GreetPerson f l ->
            // example content with the query parameters
            sprintf "Hello %s %s" f l
            |> box
            // e.g   /greet?firstname=John&lastname=Doe  -> Hello John Doe
        | Order p -> // same as above but json comes in request body
    )

Please check the documentation for more information.

Sitelets is a layer of abstraction on top of ASP.NET Core so it can work with other F# web frameworks like Giraffe or Saturn for example. Let's take a look at a Giraffe app, for starters:

dotnet new giraffe -o MyGiraffeApp

dotnet add MyGiraffeApp/MyGiraffeApp.fsproj package Sitelets

Let's add a sitelet that echoes what you write after the /echo endpoint

// ---------------------------------
// Sitelet
// ---------------------------------

type Endpoint =
    | [<EndPoint "GET /echo">] Str of string

let inferredSite =
    Sitelet.Infer (fun ctx -> function
        | Str str -> box str
    )

...

let webApp =
    choose [
        GET >=>
            choose [
                route "/" >=> indexHandler "world"
                routef "/hello/%s" indexHandler
            ]
        SiteletHelper.sitelet inferredSite
        setStatusCode 404 >=> text "Not Found" ]

Add the sitelet to the pipeline and we are done!

Although the focus is on the F# side, you can also use the Sitelets library in C# ASP.NET Core project. As an example:

public class TestSitelet
    {
        public static Sitelet<object> S =>
        new SiteletBuilder()
            .With("/hello", ctx =>
                    "Hello World from C#"
            )
            .Install();
    }

If you find any faults, please submit a ticket.

It is an open source project so anyone is more than welcome to contribute but make sure to discuss the changes before opening a PR, otherwise it might get rejected.

• Nuget
• Intellifactory