Question

I’m looking to output some HTML to a web page using F#. Any ideas?

Answer 1

To give some specific “HOWTO”, I tried creating a simple ASP.NET MVC application that implements the key parts in F#. As noted in the referenced answer, the best way to use F# for web development is to create a C# web application and move all the types that implement the actual behavior to an F# library.

Although it may be possible to create directly F# web project, there are many limitations (e.g. not perfect intellisense and possibly other issues), so managing the aspx files in C# is probably a better idea.

Here is what I did (using Visual Studio 2010):

• Create a new C# project “ASP.NET MVC 2 Web Application”. This creates a new C# project with some initial template and a few pages. I’ll ignore the page that handles accounts (you can delete it).
• There is HomeController.cs file in Controllers, which contains functionality for the homepage (loading of data etc.) You can delete the file – we’ll re-implement it in F#.
• Add new “F# Library” project and add references to ASP.NET MVC assemblies. There is a plenty of them (see the C# project), but most importantly, you’ll need System.Web.Mvc.dll and others that are referenced by this one (the F# compiler will tell you which ones you need).
• Now, add the code below to Module1.fs – this implements the original HomeController, which used to be written in C#.

The source code looks like this:

namespace MvcApplication1.Controllers

open System
open System.Web.Mvc

[<HandleError>]
type HomeController() =
  inherit Controller()

  member x.Index() =
    x.ViewData.["Message"] <- "Welcome from F#"
    x.View() :> ActionResult

  member x.About() : ActionResult =
    x.View() :> ActionResult

This is simply a re-implementation of the original C# code (creating a single class). I used the original C# namespace, so that the MVC framework can easily find it.

The file Views\Home\Index.aspx from the C# project defines the user-interface and uses the data that you set to the ViewData dictionary from your F# project.

This “HOWTO” shows how to use F# to write ASP.NET MVC application, but the steps to create an ordinary WebForms application would be essentially the same – create a C# web application and move the implementing classes to F# library, which will be referenced from the C# web application (which won’t actually contain much C# code).