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dotnet
roslyn
C#2015–2026
dotnet / roslyn

roslyn

The Roslyn .NET compiler provides C# and Visual Basic languages with rich code analysis APIs.

Languages & Compilers
Explore on GitHubRead Hacker News discussions
115Distinct people
143Mentions
1Explicit recommenders
20.8KGitHub stars
REPOSITORY AT A GLANCE

What to know before exploring

What it is

The Roslyn .NET compiler provides C# and Visual Basic languages with rich code analysis APIs.

GitHub

Where it is used

No documented product use was verified in the last source check.

What people are saying

> - I love that they are adding REPL. I really wish C# had this Here you go :) https://github.com/dotnet/roslyn/wiki/C%23-Interactive-Walkt... Also: csi.exe. Try it :)

josteink used a recommendation phrase. One indexed comment matches. This is a phrase match, not a verdict.

No classified warning is attached to this page. Read the discussions before treating silence as approval.

Also in these discussions

Mentioned in the same Hacker News threads. That is not proof they are substitutes.

This week on Hacker News

Nov 8–Nov 15 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/15/2026, 2:17:07 AM UTC.

No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.

Mentions over time

HN mentions by year143 dated mentions

Observed mentions: 2015-01-14 23:49:47 UTC to 2026-05-11 08:56:48 UTC.

01020302015-01-01 00:00:00 UTC to 2016-01-01 00:00:00 UTC (exclusive): 32 mentions; 6 submissions, 26 comments20152016-01-01 00:00:00 UTC to 2017-01-01 00:00:00 UTC (exclusive): 28 mentions; 6 submissions, 22 comments2017-01-01 00:00:00 UTC to 2018-01-01 00:00:00 UTC (exclusive): 26 mentions; 2 submissions, 24 comments2018-01-01 00:00:00 UTC to 2019-01-01 00:00:00 UTC (exclusive): 6 mentions; 1 submissions, 5 comments2019-01-01 00:00:00 UTC to 2020-01-01 00:00:00 UTC (exclusive): 6 mentions; 0 submissions, 6 comments2020-01-01 00:00:00 UTC to 2021-01-01 00:00:00 UTC (exclusive): 12 mentions; 0 submissions, 12 comments20202021-01-01 00:00:00 UTC to 2022-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments2022-01-01 00:00:00 UTC to 2023-01-01 00:00:00 UTC (exclusive): 4 mentions; 0 submissions, 4 comments2023-01-01 00:00:00 UTC to 2024-01-01 00:00:00 UTC (exclusive): 3 mentions; 1 submissions, 2 comments2024-01-01 00:00:00 UTC to 2025-01-01 00:00:00 UTC (exclusive): 11 mentions; 1 submissions, 10 comments2025-01-01 00:00:00 UTC to 2026-01-01 00:00:00 UTC (exclusive): 8 mentions; 0 submissions, 8 comments2026-01-01 00:00:00 UTC to 2027-01-01 00:00:00 UTC (exclusive): 6 mentions; 1 submissions, 5 comments. Incomplete calendar period.2026*

* An incomplete calendar period is marked with an outlined bar. Its count is not directly comparable with a full period.

Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.

View mention counts and date ranges
UTC ranges include their start and exclude their end. Select a period to filter the source evidence.
PeriodStart (UTC)End (exclusive, UTC)MentionsSubmissionsComments
20152015-01-01 00:00:00 UTC2016-01-01 00:00:00 UTC32626
20162016-01-01 00:00:00 UTC2017-01-01 00:00:00 UTC28622
20172017-01-01 00:00:00 UTC2018-01-01 00:00:00 UTC26224
20182018-01-01 00:00:00 UTC2019-01-01 00:00:00 UTC615
20192019-01-01 00:00:00 UTC2020-01-01 00:00:00 UTC606
20202020-01-01 00:00:00 UTC2021-01-01 00:00:00 UTC12012
20212021-01-01 00:00:00 UTC2022-01-01 00:00:00 UTC101
20222022-01-01 00:00:00 UTC2023-01-01 00:00:00 UTC404
20232023-01-01 00:00:00 UTC2024-01-01 00:00:00 UTC312
20242024-01-01 00:00:00 UTC2025-01-01 00:00:00 UTC11110
20252025-01-01 00:00:00 UTC2026-01-01 00:00:00 UTC808
2026 (partial)2026-01-01 00:00:00 UTC2027-01-01 00:00:00 UTC615

From the project README

An excerpt from the repository, fetched Nov 13, 2026.

Read the project’s introduction
The .NET Compiler Platform Roslyn is the open-source implementation of both the C# and Visual Basic compilers with an API surface for building code analysis tools. C# and Visual Basic Language Feature Suggestions If you want to suggest a new feature for the C# or Visual Basic languages go here: dotnet/csharplang for C# specific issues dotnet/vblang for VB-specific features dotnet/csharplang for features that affect both languages Contributing All work on the C# and Visual Basic compiler happens directly on GitHub. Both core team members and external contributors send pull requests which go through the same review process. If you are interested in fixing issues and contributing directly to the code base, a great way to get started is to ask some questions on GitHub Discussions! Then check out our contributing guide which covers the following: Coding guidelines The development workflow, including debugging and running tests Submitting pull requests Finding a bug to fix in the IDE or Compiler Finding a feature to implement in the IDE or Compiler Roslyn API suggestions should go through the API review process Community The Roslyn community can be found on GitHub Discussions, where you can ask questions, voice ideas, and share your projects. To chat with other community members, you can join the Roslyn channel on the CSharp Community Discord. Our Code of Conduct applies to all Roslyn community channels and has adopted the .NET Foundation Code of Conduct. Documentation Visit Roslyn Architecture Overview to get started with Roslyn’s API’s. NuGet Feeds The latest pre-release builds are available from the following public NuGet feeds: Compiler: https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-tools/nuget/v3/index.json IDE Services: https://pkgs.dev.azure.com/azure-public/vside/_packaging/vssdk/nuget/v3/index.json .NET SDK: https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet5/nuget/v3/index.json Continuous Integration status Builds Branch Windows Debug Windows Release Unix Debug main Desktop Unit Tests Branch Debug x86 Debug x64 Release x86 Release x64 main CoreClr Unit Tests Branch Windows Debug Windows Release Linux main Integration Tests Branch Debug x86 Debug x64 Release x86 Release x64 main Misc Tests Branch Determinism Analyzers Build Correctness Source build TODO/Prototype Spanish MacOS main .NET Foundation This project is part of the .NET Foundation along with other projects like the .NET Runtime.
Read the full README on GitHub

What Hacker News says

28 sources
Metasyntactic·Nov 25, 2016
Hey Anchor, I'm https://github.com/CyrusNajmabadi a developer on the Roslyn team, and a primary developer around many of the new features Kasey demo'ed here. You're definitely correct that many of these things have already appeared in Resharper. However, that wasn't the point of us building them. We invested in the Roslyn platform many years ago so that not only could we share and leverage code across all our languages, but so that other people could plug in as well to add the sorts of enhancements they would like. Currently, We've moved C#, VB, TypeScript, JavaScript, and now Xaml, onto the Roslyn platform. Because of this (note that some of this is bleeding edge), not only can we all share a common infrastructure for things like Find-References, IntelliSense, and Refactoring, but 3rd parties can now plug in as well and add their own
Read the rest
capabilities. For example, all the refactorings we've offered are ones that others could have as well. We just happen to think that, over time, we should continually be improving the core set we provide so that you can get a highly capable and powerful experience out of the box without necessarily having to go install a lot of extra plugins. Of course, if you do find plugins (including resharper) that you find valuable, then we want you to def go out and enhance your experience with them. I hope you get a chance to try this stuff out. As always, please file feedback/issues on github.com/dotnet/Roslyn Thanks!
In .NET Productivity Improvements [video]
int_19h·Nov 16, 2016
> Likewise Java's OOP enums (basically singletons) are something I miss too. C# guys are working on adding full-fledged pattern matching to the language: https://github.com/dotnet/roslyn/blob/features/patterns/docs... and there's a concurrent proposal for ADTs: https://github.com/dotnet/roslyn/issues/6739 Given the velocity of adding new features in C# these days, these will come sooner rather than later (indeed, some basic pattern matching is already in C# 7).
In Google joins .NET Foundation as Samsung brings .NET support to Tizen
jongalloway2·Oct 7, 2016
For that example, they're showing Visual Studio opening the Roslyn repo (https://github.com/dotnet/roslyn). Without any package restore, that's 200MB / almost 12k files. Keeping in mind that Visual Studio isn't a simple text editor, it's a code editor that provides code-based IntelliSense, extensions, integrated debugging, etc., I'd say 30 seconds isn't too bad, especially considering some websites these days take nearly that long to finish rendering.
In Announcing Visual Studio “15” Preview 5
ulber·Sep 15, 2016
Other people are already flooding you with counterexamples, but I'll add to the pileup: Z3 (https://github.com/Z3Prover/z3) is the Satisfiability Modulo Theories (SMT) solver to use. It is such a quality piece of software and it's amazingly easy to find help on StackOverflow from the main developers. Z3 really is the default choice for an SMT solver these days (i.e. you only reach for other solvers when you really have to). Roslyn (https://github.com/dotnet/roslyn) is the C# (and VB) compiler as a library. Useful for doing code analysis and code generation for a modern imperative language. Roslyn is a whole lot easier to get started with than integrating Clang/LLVM into a project, so it really lowers the barrier of entry for lightweight program analysis projects.
In Microsoft is now the leading company for open source contributions on GitHub
waterphone·Sep 5, 2016
Here are a few random examples of such absurdity I found in a several minute search. https://github.com/opal/opal/issues/941 https://github.com/kickstarter/rack-attack/pull/181 https://github.com/graphite-project/graphite-web/issues/1569 https://github.com/dotnet/roslyn/pull/3507 https://github.com/Droogans/unmaintainable-code/pull/20 https://github.com/zendframework/zend-expressive/pull/340 https://github.com/assemble/assemble.io/issues/163 https://github.com/braydie/HowToBeAProgrammer/issues/68 https://github.com/airbnb/javascript/pull/698 https://github.com/lighthouse-labs/clock-tower/pull/87 https://github.com/smalltownheroes/bikini-girls-with-machine... https://github.com/kubernetes/kubernetes/issues/27430 https://github.com/ardanlabs/gotraining/issues/75 https://github.com/antirez/redis/issues/3185 https://github.com/syl20bnr/spacem
Read the rest
acs/pull/3484 https://github.com/TryGhost/Ghost/issues/5889 https://github.com/twolfson/sexy-bash-prompt/issues/56 http://web.archive.org/web/20151030100136/https://github.com... https://github.com/pickhardt/betty/issues/11
In Inclusivity Is a Joke
zamalek·Aug 25, 2016
> But is C# really a language you want if that is important to you. C# is used by hundreds if not thousands of games by ways of Unity and is therefore demonstrably good enough in this scenario. Furthermore, just because a language is not C++ does not mean you shouldn't take every opportunity to give programmers tools to write fast code - at the end of the day I doubt anyone would be interested in a language that is purposefully slow. Performance was a core feature of the language (yes, yes, it's managed) from day 1 with unsafe - it's nice to see further improvements in that department. Use C++ when you need to, definitely, but when you're copying about 256 bytes around for a trivial world-view-projection matrix multiplication[1] you have a problem. [1]: https://github.com/dotnet/roslyn/issues/10378#issuecomment-2...
In What’s New in C# 7.0
Eyas·Aug 25, 2016
This was a concern of mine as well, as you can see in the discussion of scope changes for pattern variables [1], the C# checks for definite assignments handle this. So: if (o is int i) { f(i); } use_int(i); // <-- error: variable `i` is not definitely assigned But then if you have: if (o is int i || (o is string s and int.TryParse(out i)) use_int(i); We know that `i` is definitely assigned at that location. [1]: https://github.com/dotnet/roslyn/issues/12597
In What’s New in C# 7.0

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