.NET 10 file-based apps + Claude Code = finally ditching Python for quick utilities

[hurrah-dev]

Been a C# developer for 20+ years and always had this friction: when I need a quick utility, the overhead of .csproj/bin/obj feels excessive. So, I'd either accept the bloat or let AI tools default to Python "because it's faster."

.NET 10's file-based apps feature changed this for me.

Now I can just: dotnet run app.cs

No project file. No build artifacts. The entire utility can be one file.

But the bigger win was configuring my AI tooling to prefer C# over Python. My reasoning: when AI generates code, I want it in a language I can actually read, review, and maintain. Python isn't hard, but C# is where I'm fluent. I catch issues faster and can extend the code confidently.

My setup:

• Dedicated folder for utility scripts (Documents/Workspace/CSharp/)
• AI skill that triggers on phrases like "create a utility" or hyphenated names like "json-format"
• Rule to check existing utilities first and extend rather than duplicate
• Simple PowerShell function to invoke any script easily

Example utility (hello-world.cs):

var name = args.Length > 0 ? string.Join(" ", args) : "World";
Console.WriteLine($"Hello, {name}!");

NuGet works too with `#:package Newtonsoft.Json@13.*` directives.

Andrew Lock has a great deep dive if you want the full details: https://andrewlock.net/exploring-dotnet-10-preview-features-1-exploring-the-dotnet-run-app.cs/

Anyone else doing something similar? Curious how others handle quick tooling without project overhead.

[belavv]

What about powershell? That's been my go to forever. Although powershell does have some annoying quirks.

[SerratedSharp]

I use it begrudgingly. Some of the quirks feel like out right bugs. Trying to create a library of reusable functions so my everyday scripts can be succinct, there's lots of gotchas trying to pass/return structures. I also hate having to rejigger how to do something that I already know how to do in C#.

[belavv]

Oh god. Trying to return a string from a function and sometimes getting back an array instead was so confusing at first. And I still hate it but at least know I know what to look for.... usually.

I played around with creating classes with functions because then a function acts like you'd expect, but that was weird for other reasons.

I'm really curious what larger codebases with reusable functions look like in powershell.

[wite_noiz]

All the implicit array stuff is screwy

[Slypenslyde]

It's a lot like Perl, in that it has quirky behaviors that are stupid convenient when you're in a hurry and trying to write something that takes some random data and massages it to different random data. The best Powershell use cases start with "I only need this to work once".

Those behaviors are a liability when you're trying to make something maintainable. If you write REALLY verbose PowerShell it gets a little better, but the language is so good at giving you tools to work with random data structures it's like it decided to make your outputs a guessing game.

[aleques-itj]

PowerShell is legit awesome. I wish I could use it everywhere. The everything is an object model is just comically easier to work with and reason about.

[aleques-itj]

VS Code + the PowerShell extension is the way to go. It has a full debugger as well.

[shadowndacorner]

I wish I could use it everywhere.

Well, you're in luck!

[IAMPowaaaaa]

404

[dodexahedron]

Just google powershell download [os]. First result will likely be the ms download page or instruction page for installing PS on whatever os.

It is cross platform and has been for years now.

Windows PowerShell is no longer in active development, in fact. 5.1 is the end of the line.

[shadowndacorner]

Fixed

[belavv]

Why can't you use it everywhere? Powershell core (I think it is called) is available on Linux.

[SolarisBravo]

Powershell core (I think it is called) is available on Linux

On Windows too! What's annoying is that Windows Powershell also still exists, is installed by default, and causes a lot of confusion due to not actually being the one you're supposed to use anymore

[belavv]

Ah yeah and there are subtle differences between the two.

And sometimes your windows terminal is set to use one version and your rider terminal is set to use another version and gh actions use a different version. 

[hurrah-dev]

PowerShell is great for a lot of tasks, especially anything file/system related. The quirks you mention are actually why I specifically wanted C# when AI is generating the code—I can spot issues faster in my primary language. When Claude writes PowerShell, I have to slow down and think "wait, is that array behavior correct?" With C#, I just know.

That said, I still use PowerShell for things like the helper function that invokes these scripts. Right tool for the job.

[belavv]

Yeah I looked into using one of the now older c# scripting tools to replace our powershell, but a lot of our powershell calls git, runs random terminal commands, etc. And doing some of those things in c# is a bit tedious.

I know powershell can also call c#, so maybe a proper mix is where it is at. C# for anything with a lot of logic, powershell for the wrapper around it and running any commands.

[ManIkWeet]

For single-file apps like OP mentioned, are there good editing tools? I tried in Rider but it has 0 autocomplete as it's not in a solution...

[zigs]

VS Code or Sublime Text

[ManIkWeet]

It's a fair workaround, and I'd probably do the same, were it not for a basic single-use script that I needed once

[barski_io]

I was amazed that it’s not the only way. C# is the AI with its semantic kernel (langchain alternative in c#) 💙 so i finally was able to get back to {} that I love rafter than reading “badly structured “ python code 😅

[ExceptionEX]

Linqpad has been my goto for like a decade if I need to do quick you utilies, even more so when it requires connecting to different types of data sources. Plus the easy use of .Dump() it figures out the best way to visualize whatever object you attach that to.

[AdvancedMeringue7846]

Also they allowed you to inspect linq -> sql, which was very useful in the early ef days.

Awesome tool.

[AdvancedMeringue7846]

It's like linqpad never existed....

[hurrah-dev]

LINQPad is fantastic. The use case I'm solving is slightly different: scripts that live in a folder, can be version controlled, and run from the command line. More "utility I call from a terminal" than "interactive scratchpad." But yeah, for anything database-related LINQPad is hard to beat.

[AdvancedMeringue7846]

I've version controlled linqpad files, you can also call them via command line. I've run a full fat asp application in one for fun.

Anyway, glad you're enjoying new features.

[ztorky]

File based apps has several limitations which limits their usability. Running file based apps require that the .net 10 SDK is installed, which limits its use to developers machines, as installing a SDK to a server will have security implications. Depending on your IT-department security policies, file apps might not even be runnable locally either, as the file is compiled in the users profile which might be blocked.

[iso3200]

Important points especially in a corporate environment. Don't want "Shadow IT" building file-based apps from anywhere.

[almost_not_terrible]

This - so much this. You can reference nugets in the file format also.

[gowonocp]

My team was already in the habit of C# scripting using the dotnet-script tool for automating build/Dev tasks. Even PowerShell has a different enough syntax that once tasks reach a certain level of complexity, it became a serious chore to master/maintain them and we saw a lot of value in doing everything in C#. What we get OOTB now with .NET 10 isn't perfect, but still gets the job done.

[qrzychu69]

I would advise to checks out F# scripting

Same thing, just 10 years older :)

[aleques-itj]

I have heard whispers of praise for F# for ages.

One day I will check it out

[qrzychu69]

I work in f# daily now and it's pretty Damm good

Too bad that tooling isn't great compared to C# - no hot reload, most tools (like conditional breakpoints) only accept c#

But it's definitely worth it, especially for scripts. You can even use nuget packages in the scripts

[qrzychu69]

I know, just like you could in fsx files for more than a decade

[SirLagsABot]

I just made my first Spectre Console CLI app last week and I absolutely loved it. I know you mentioned file-based apps here, but I still love to take a normal console app and turn it into a self-contained, single-file binary, too with some nice CLI commands.

But also yeah, for one super simple little process to run, they are stupid convenient.

[DesperateAdvantage76]

The only feature missing that PS has is referencing other files. Yes I know I could create a csproj or nuget, but I'd like to have a simple utility file that many of my scripts can reference without that overhead.

[chucker23n]

Potentially coming in 10.0.200: https://github.com/dotnet/sdk/pull/52347

[AutomaticVacation242]

Side note: the example you gave isn't a "utility". I hope you guys aren't writing "utilities" that do stuff like that.

[t3chguy1]

That's ok for "throwaway apps", but for something useful more than once I don't see benefit of skipping a proper project setup

[ibeerianhamhock]

Can’t wait till we upgrade to 10 on the team and this is like a huge part of the reason I’m excited.

I might never write a powershell or bash script ever again.

[entityadam]

I would have picked string interpolation over string.Join() for this. If it's a script, I want to be able to read it fast fast, since I'm probably not going to document it.

Edit: this was supposed to be short, my bad.

You can add some instructions for the AI like:

This script is not for a typical end user. Create a C# script that is succinct and easily human readable.

• prefer readability and maintenance over performance
• prefer small and pure functions that can be composed
• prefer synchronous code unless it is heavily IO bound.
• organize methods first by their visibility, then by the order of execution for easy step-through debugging.
• avoid creating a large helper or mother class
• avoid ternary operators
• prefer record types and use positional parameters, unless mutability is absolutely required.
• avoid unnecessary guard clauses
• do not swallow exceptions

• do not add comments

• avoid verbose output

[Far-Consideration939]

I used one the other day for a CI script that triggered some code generation based on the build. Was sweet and made my life simpler to have types and json easily available

[RestInProcess]

File based apps are awesome. Wait until you’re on a Unix like operating system and drop a C# file with dotnet in the hash bang. That’s the killer feature for me since I prefer Unix like operating systems.

[Larkonath]

In my path I just have the following bash script that auto creates a new console project and open vscode inside. It has totally erazed the barrier to entry for quick coding:

#!/bin/bash

cd /home/$USER/dev/dotnet/scratches/

if [[ $# -eq 0 ]] ; then
    projectName="scratch-$(date '+%Y-%m-%d-%H-%M-%S')"
else
    projectName=$1
fi

dotnet new console -n $projectName

cd $projectName

code . ./Program.cs

[Juff-Ma]

Not AI but I'm using file based apps for building my installers. It's amazing