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Mads Torgersen: C# in 2025 and Beyond

London ․NET User Group

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  • Recommended by 1 person: 1 in engineering communities.
  • Presented by Mads Torgersen, lead designer on the C# team at Microsoft

Intermediate. Assumes working knowledge.

11K views1 year ago1 recommendation

Programming languagesC# and .NETLanguage design and type systems

Mads Torgersen discusses upcoming C# features under consideration, including extension properties, union types, and collection literals, explaining their design trade-offs.

In this deep-dive session recorded at NDC London in January 2025, Mads Torgersen, lead designer on the C# team at Microsoft, talks through some of the patterns and proposals that are under consideration for the next version of C# and .NET. It's a very early look at extension properties, union types, a new proposed syntax for collection literals - but it's also a fascinating insight into how features like this get added to the language, as Mads talks us through multiple different syntax options and possible approaches, explaining the trade-offs of each, and the challenges of adding new features and keywords to the C# language without breaking anybody's existing code. Recorded at the London .NET User Group meetup, January 28 2025, at the QEII Centre in London. Huge thanks to NDC Conferences for supporting this event, and to Mads for taking the time to talk to us.

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1 person recommends this

What people say. Recommended as an interesting insight into how C# features get proposed, evolve, and make it into the language.

Moments people linked to

u/dylanbeattiein r/dotnet • Recommends

Mads Torgersen on the future of C# at the London .NET User Group (video) Back in January, the London .NET User Group (disclosure: I'm one of the organisers) hosted a session with Mads Torgersen - lead designer on the C# language team at Microsoft - about the next version of C#. It's a really interesting insight into how features get proposed, evolve, and eventually make it into the language (or not) - and along the way Mads shows a bunch of proposals for new syntax and structures which *might* be part of C# 14 when it ships in November. The video is up on our YouTube channel now: [video
75View on Reddit

u/zenylin r/dotnet • Mentions

On “Reddit asks the expert - Stephen Toub”

Mads Torgersen discussed unions in a recent presentation: link to this video The language design team have done a lot of work on unions recently (visible from the LDM notes on GitHub). In the presentation, Torgersen says that plans are to start work on implementing unions after the release of .NET 10, and if everything goes optimally, the first parts of unions will release with .NET 11 (November 2026).
17View on Reddit

u/zenylin r/dotnet • Mentions

On “Discriminated Unions on ASP.NET 11 roadmap”

Yup, this aligns with what Mads Torgersen (C# language design lead) said in a presentation presentation last year. He discussed DUs (among other things), and said that, if everything goes perfectly, the hope is for the first parts of DUs to arrive with C# 15. Link: link to this video
8View on Reddit

u/CookingAppleBearin r/dotnet • Mentions

On “Nominal Type Unions for C# Proposal by the C# Unions Working Group”

Oh man, I forgot about that syntax they proposed over a year ago! Looks like this is the talk you were referencing: link to this video And I think Mads addresses why they had to move away from that syntax here: link to this video Reading through the discussions (there's a lot), it seems like the reasoning was two-fold - 1) splitting apart the "roles" feature from extensions and 2) the previous syntax didn't support use cases the design team felt were *required* Personally, I think the old syntax looks very "not" C# and the new looks very C#. It would be nice to have a single block that handles everything, but it appears that wasn't possible. I do love extra levels of organization so I kinda appreciate the extr…
1View on Reddit