LDM Notes for September 10th, 2025

[333fred]

https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-09-10.md

Agenda

• Unions overview

[TonyValenti]

Maybe this makes too much GC garbage, but I think you could create a Box(of T) class and, when working with large structs, create a new box, set its value, and then set the value of the union to the box.

[mattwar]

There is already a class StrongBox<T> that does what you want. However, both boxing a struct to object and using this type would result in similar allocations. The runtime is better optimized to deal with collecting boxed objects though.

[DavidArno]

"Today, we took time for a broad overview of the various union proposals being considered for C#, as compiler team members are about to start implementation."

I let out a little squeak of genuine excitement when I read that 😁

[333fred]

I figured some people might like that line.