Tag: csharp

Back in 2023, I wrote about discriminated unions in C# and how C# developers had to work around the lack of language support using things like ASP.NET Core’s Results<> type or the OneOf NuGet package. Real C# language support (csharplang issue #113) had been open for years with no sign of a proper solution. Well, the wait is over. C# 15, shipping with .NET 11 (preview), introduces first-class union types. Let’s have a look.

When writing libraries and frameworks that others are using, it’s sometimes hard to convey that a given API is still considered “experimental”. For example, you may want to iterate on how to work with part of the code base with the freedom to break things, while still allowing others to consume that code if they are okay with that.

Discriminated unions have been a long-standing request for C#. While F# users have had discriminated unions for years, C# developers will have to wait a bit longer. What discriminated unions allow you to do is tell the compiler (and other tooling like your IDE) that data can be one of a range of pre-defined types.