https://cekrem.github.io/tags/csharp/Recent content in Csharp on cekrem.github.ioHugoen-usMon, 09 Nov 2026 00:00:00 +0000https://cekrem.github.io/posts/csharp-15-union-types/Mon, 09 Nov 2026 00:00:00 +0000https://cekrem.github.io/posts/csharp-15-union-types/<p>.NET 11 launches this week at <a href="https://dotnet.microsoft.com/en-us/conf" class="external-link" target="_blank" rel="noopener">.NET Conf</a>, and with it comes C# 15. The headline feature, at least for someone like me, is <a href="https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/builtin-types/union" class="external-link" target="_blank" rel="noopener">union types</a>. People have been asking for discriminated unions in C# for years, and now there&rsquo;s a <code>union</code> keyword in the language.</p> <p>A disclaimer before we start: <strong>C# is not my home turf.</strong> I write Elm on the frontend, I&rsquo;ve done a fair bit of Kotlin, and I <a href="https://cekrem.github.io/posts/why-i-hope-i-get-to-write-a-lot-of-fsharp-in-2026/" >hope to write a lot more F#</a>. So this is an outsider looking at a feature I care about, in a language I don&rsquo;t use daily. If I&rsquo;ve missed some well-known C# idiom below, I&rsquo;d genuinely like to hear about it.</p>