Why Winforms F#?

I'm not really sure. I was reading through an older F# book that made a lot of small examples in winforms, and since I only have .NET core on my machine right now, I wanted to see if it was possible, and couldn't find any easy resources on how to do it.

Getting Started

So we are going to assume that you already have dotnet core installed on your machine. If not head over asp.net and get it.

First just make a new F# console app.

dotnet new console -lang F#

The next thing that you are going to have to do is add a <UseWindowsForms>true</UseWendowsForms> to the PropertyGroup in your fsproj file.

You may also have to add a -windows to your <TargetFramework> depending on your dotnet sdk version.

It should look like this

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net5.0-windows</TargetFramework>
    <UseWindowsForms>true</UseWindowsForms>
  </PropertyGroup>

  <ItemGroup>
    <Compile Include="Program.fs" />
  </ItemGroup>

</Project>

Next, head over to your Program.fs and make the following changes.

Add an open System.Windows.Forms to the top.

You will also need to ad STAThread to your attribute tag on the main.

This should be how it looks now.

// Learn more about F# at http://docs.microsoft.com/dotnet/fsharp

open System
open System.Windows.Forms

// Define a function to construct a message to print
let from whom =
    sprintf "from %s" whom

[<EntryPoint; STAThread>]
let main argv =
    let message = from "F#" // Call the function
    printfn "Hello world %s" message
    0 // return an integer exit code

With that you can try to make simple forms and run it and it should work.

Here is my HelloWorld form

open System
open System.Windows.Forms

[<EntryPoint; STAThread>]
let main argv =
    let form = new Form (Width=400, Height=300, Text="F# Forms")
    form.Show ()
    Application.Run form
    0 

then just dotnet run and it should work.