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CSharpRepl: C# REPL with syntax highlighting and intellisense (fuqua.io)
142 points by aragonite on May 23, 2024 | hide | past | favorite | 43 comments


There is an alternative of LinqPad. It does not have a lot of features, but it is good enough for testing code snippets.

https://github.com/roslynpad/roslynpad


When it comes to C# REPLs I absolutely adore LinqPad, although recently it's felt like I've had to buy licenses for it increasingly often which I've found annoying.

If any other REPL can get to a point where it can rival LinqPad in functionality then it'll be an absolute winner.

The key features linqpad has that I'd need from any replacement:

* Securely store secrets

Util.GetPassword prompts the user for the password if it's not in it's store. Leverages the windows user credential store.

* Keeps the process running

This is absolutely key, it keeps alive the process even after the script has finished, so you can easily attach a debugger / profiler to it when the script isn't running, then start the script again. It also means you can use AppDomain.CurrentDomain.SetData to cache expensive setup if you're trying to profile something.

* Quickly switch between expression / statements / program mode

It'll intelligently work out if you've written a single expression vs multi-line statements, and you can switch to "program" and it'll wrap what you've done so far in a Main stub.

* Easily define default App.Config files, default namespaces, default nuget packages.

After finally getting a fiddly setup working, there's a "Use as default for new queries" button which is very convenient. Also the "clone query" functionality is similarly useful for copying not just the C# text but all the background namespace declarations, references, config, etc.

And that's about it. I barely use the database connection and exploration side, but I do use it daily for hooking into DLLs to quickly test changes to our internal projects.


Great to see LINQPad getting some love. Wish it had a fully functional trial so outsiders can see the real thing before paying. Otherwise, the free version is crippled and boring.

Made this video to show LINQPad and getting OAuth tokens from the Spotify api.

https://www.youtube.com/watch?v=g2C1SXfTHXI&t=30s


RoslynPad support user input with `Console.ReadLine()`, but that's about it. For me personally it does everything I need for scripting C#. For anything more serous I usually create full program and a bat/sh file to execute it in a conveniently.


I used Basic, Pascal, C++, C, Javascript, Python, Java and C#.

C# is my favorite language because is relatively easy to write something without having to write a lot and there's relatively little boiler plate and ceremony.

On top of its imperative foundations there were added some functional capabilities that are integrated very well.

What is als likeable is there are a ton of learning materials for those who are interested, a ton of libraries and frameworks and the community being helpful.

Also, C# can be used in about every domain, web backend, web fronted, desktop, small utilities, games, mobile and even microcontrollers.

What I dislike about C# is that every file is also an object and I rather like a less OOP approach.

Also, there are features the community asked for years, like algebraic types and even though people working on the language implementation recognized their importance, they still didn't find their way in the language.

My favorite update to C# would be if it doesn't force so much object oriented workflow. Even C++ lets you work in a procedural way.

Another.NET language I like is F# but I didn't invest much time in it because I don't have where to use it for work.


> Another.NET language I like is F# but I didn't invest much time in it because I don't have where to use it for work.

F# mostly replaced bash/powershell for me.


I have been dabbling with F# for scripts as well. The F# REPL (FSI) and .fsx files make it really easy to hammer something out and share.


I just started learning C# while tinkering with Monogame.

It's a really nice language to use, I'm quite surprised.


C# is an absolutely excellent language, and continues to gradually improve.

Because I had to check this myself: Monogame is not tied to mono! It claims to support dotnet 8, so it looks suitably current and maintained.

It is annoying that Microsoft had their own perfectly adequate game framework which they binned at one of the transitions https://en.wikipedia.org/wiki/Microsoft_XNA


monogame is pretty much the continuation of XNA although they have added more stuff.

There is another framework called FNA that I've not used personally but I've heard it tries to match XNA exactly while monogame is a bit more forward looking. So FNA is good for porting forward your older XNA games.


C# is really an awesome language, it’s come such a long way. I know it used to be a pain and not very cross-platform friendly, but nowadays it’s a dream. Shoutout to Rider as the best IDE for it lol


I've done C# for a while and I really love what can be done with DI & reflection for cool cross cutting abilities.

I want to branch out to native stuff like C++ & Rust for memory management stuff, but they don't seem to come close in terms of the reflection abilities or probably the function is there, but just a nightmare to work with.

Anybody have any thoughts/opinions?


Take a look at System.Memory; it’s quite possible you don’t need to leave C# to do what you need with memory.


C# was my first language so I am biased, but it continues to be my favorite language out of any I've tried.


As someone who first learned to program in the early 80's, C# is far from my first language. But it is my favorite as well!


Give F# a try as well if you have some time. It's even better, and can do anything C# can do!


The core is very good, the OOP aspects can be really quite poor.

Let me write a function without 50 tokens of boilerplate!


You just need to put them in a static class to act as a name space. What is the big deal?


Love C# but

  public static implicit operator ClassA(ClassB b)
Is very verbose. There are probably worse offenders. C# devs also love to add access modifiers even when its not needed. For example, private for anything that is meant to be private or the suffix `Async` even though you don't have a sync version of a method.


The private keyword is needed because the default access is public to the same assembly. Usually that's very different from private.

As for the implicit cast, two extra tokens in an uncommon case doesn't seem so bad when you consider all the nice common things like var, the lambda syntax, initializers, pattern matching, LINQ, delegates, etc. etc.


Default visibility for type members is private, default visibility for not-nested types is internal.

Defining implicit cast operators frequently (especially ClassA -> ClassB) might be a sign that a better implementation is required. In practice, it's not done often.

Agree on unncessary Async suffix. It is a common mistake (it is one) to add it for methods that cannot or will not offer non-async variants.


In a sense, internal is just another way of viewing it as “private to the assembly”. If i don’t need something to be reached by another assembly, then typing `internal` when not necessary is just too much.

Note: I’m ignoring <InternalsVisibleTo> csproj property.


1. It's very long winded.

2. It encourages everyone to think about nouns rather verbs.


What’s wrong with nouns?


https://steve-yegge.blogspot.com/2006/03/execution-in-kingdo...

It's not as extreme as java but the smell is there.


I honestly did not find that blog to be a compelling argument. Maybe something more recent or more serious would help explain better.


Ultimately it just clashes with my taste.

I don't really know how else to enunciate it anymore than how I don't like Taylor swift music or whatever.


Yeah, I don't know, the argument here I think is just dated if I'm interpreting it correctly. There's nothing there in Java that forces you to make classes that are actions or verbs. You could do the same in any language that has classes. Java has long since supported lambdas and functions that can be passed around.


Just have an editor macro that expands "def" to "public static void"


Can you make an example of “poor”?


My concerns are mostly in the space between files and whole projects so I can't be super precise but one micro-scale thing that really worrys me is the lack of any discriminated unions in the language.

There a time when class hierarchies are ugly but fine, completely fine, and genuinely a bit dangerous: C# doesn't seem to have an option for the latter


How does it compare with LinqPad, polyglot notebooks, csi.exe?


The author has some comments on this on GitHub:

https://github.com/waf/CSharpRepl?tab=readme-ov-file#compari...

Even though it's not as feature-rich as linqpad's Dump() method, personally I find the ability to pretty print any object ("detailed view"[1]) by pressing ctrl+enter really convenient. E.g. try typing in

  new Uri("https://news.ycombinator.com")
(without semicolon), then pressing ctrl+enter.

[1] https://github.com/waf/CSharpRepl?tab=readme-ov-file#:~:text...


Looks quite nice, specially since VSCode lacks interactive panes.


VSCode has plugin for polyglot notebooks https://code.visualstudio.com/docs/languages/polyglot


I think you can run C# in the debug console while debugging, at least.


Is it capable of UTF-8? I couldn't for the life of me get the F# REPL to read UTF-8.


What do you mean? With dotnet fsi? I just tried it and it reads UTF8 just fine, at least in windows terminal.


It doesn't change the output encoding by default, but if you manually set it to UTF8 it works. (IE: Console.OutputEncoding = System.Text.Encoding.UTF8;)

That might be all you need to fix the F# REPL too.


If you mean problems having to do with assigning "..."u8 UTF-8 string literals to variables, there's this workaround:

https://github.com/waf/CSharpRepl/issues/318#issuecomment-21...


There's also LinqPad.


NetPad for the OSS version. works great. https://github.com/tareqimbasher/NetPad


Can't stop reading it as "shrapnel", especially with "intellisense" just below




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