dotnet actions: C# scripting to the rescue

What a monumental release for .NET scripting is .NET 10! The long journey that started with C# 9 top-level programs has finally culminated in a full-fledged scripting experience that leverages the entire .NET ecosystem in .NET 10:

1. File-based apps go beyond just C# statements and now supports #:sdk, #:package and #:property directives that allow the full breadth of .NET SDKs and NuGet packages to be used in scripts without the need for a project file.
2. SmallSharp is a tiny NuGet package / MSBuild SDK that teaches Visual Studio how to edit multiple file-based apps in a single project, using the complete capabilities of the IDE, including IntelliSense, debugging, refactoring, etc.
3. dnx tool execution allows running tools without having to first install them, npx-style.
4. runcs is a tiny dotnet tool that makes it easy to run (and auto-update) file-based apps hosted on GitHub, GitLab and Azure DevOps.

This means that with the .NET 10 SDK, you can run the following sample script without any prior setup:

#:package Spectre.Console@0.50.*
using System.Runtime.InteropServices;
using System.Text;
using static Spectre.Console.AnsiConsole;

// Ensure even the dev console on Windows can display UTF-8 characters.
if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
    System.Console.InputEncoding = System.Console.OutputEncoding = Encoding.UTF8;

MarkupLine("[blue]Hello[/] :globe_showing_americas:!");

And since the source for it is hosted on GitHub, you can simply run it with:

dnx runcs devlooped/actions@main:hello.cs

This will download the script, restore its dependencies, compile it and run it, all in one go! And the next time you run it, it will check for updates and download the latest version if available.

This is something that might be supported out of the box by dnx in the future:

This is a game-changer for automation and scripting with .NET, as it combines the best of both worlds:

• The simplicity and ease of use of scripting languages like PowerShell, Python or Bash.
• The power and versatility of a full-fledged programming language like C# and the .NET ecosystem
• The productivity and convenience of modern IDEs like Visual Studio.

I have done my share of GitHub Actions and I’m totally willing to sacrifice the Marketplace visibility for the extreme simplicity of just invoking a C# script from a repo from my GitHub workflows.

It means you can replace my existing which-dotnet action:

      - name: 🤌 dotnet
        uses: devlooped/actions-which-dotnet@v1

with the equivalent that runs the which-dotnet.cs script:

      - name: 🤌 dotnet
        run: dnx runcs devlooped/actions@v1:which-dotnet.cs

For quickly sharing little programs with friends and colleagues, it’s also a great way to avoid having to create a nuget package, push to nuget.org, only so they can run dnx mytool and have it auto-update whenever I push a new version. The combination of dnx, runcs and file-based apps is a killer combo for sharing code snippets that just work and stay up-to-date.

I have blogged on SmallSharp before when I released 2.0. The latest 2.1 release extends support for file-based apps by also supporting the #:sdk directive, which means you can now use any .NET SDK in your scripts, not just the default one. It requires switching to using SmallSharp as an SDK though:

<Project Sdk="SmallSharp/2.1.0">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net10.0</TargetFramework>
    <LangVersion>preview</LangVersion>
  </PropertyGroup>

</Project>

Exciting times for all .NET developers and enthusiasts! Happy C# scripting 🚀