Projects and NuGet Packages

Scripts are great for exploring; applications and libraries live in projects, built by the dotnet command-line tool.

Creating a solution

dotnet new sln -n Shop
dotnet new classlib -lang F# -o src/Shop.Core
dotnet new console -lang F# -o src/Shop.Cli
dotnet new xunit -lang F# -o tests/Shop.Tests
dotnet sln add src/Shop.Core src/Shop.Cli tests/Shop.Tests
dotnet add src/Shop.Cli reference src/Shop.Core
dotnet add tests/Shop.Tests reference src/Shop.Core

This gives a class library for your domain code, a console app that uses it, and a test project — a common layout for real F# work.

The .fsproj file

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

  <PropertyGroup>
    <TargetFramework>net10.0</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <Compile Include="Money.fs" />
    <Compile Include="Orders.fs" />
    <Compile Include="Library.fs" />
  </ItemGroup>

</Project>

Unlike C#, F# lists every source file explicitly, in compilation order: Orders.fs can use Money.fs, but not the other way round. Editors keep this list for you ("Move file up/down" in Ionide and Rider). This rule prevents circular dependencies and makes a codebase easy to read from top to bottom.

NuGet packages

NuGet is .NET's package manager, with hundreds of thousands of packages at nuget.org:

dotnet add package FSharp.Data
dotnet add package FsToolkit.ErrorHandling
dotnet list package
dotnet restore

dotnet add package adds a <PackageReference> line to the .fsproj. Every C# library works from F#, plus F#-specific ones such as FSharp.Data (type providers), FsToolkit.ErrorHandling (result helpers), Argu (command-line parsing), Thoth.Json and FSharp.SystemTextJson (JSON), Expecto (tests), and Giraffe (web).

Packages in scripts

Scripts can reference packages directly — no project needed:

// illustrative: downloads the package on first run
#r "nuget: Humanizer"

open Humanizer

printfn "%s" ("some_database_column".Humanize())
printfn "%s" (System.TimeSpan.FromMinutes(90.0).Humanize(2))

Some database column
1 hour, 30 minutes

Pin a version with #r "nuget: Humanizer, 2.14.1" so the script keeps working the same way. #load "Helpers.fsx" includes another script file.

Everyday commands

Paket is an alternative dependency manager popular in parts of the F# community; plain NuGet with PackageReference is the default and works well for most projects.