C# 9 Support for Unity

C# 9 has just been released alongside with .NET 5. Will the support for C# 9 rolled out to Unity soon?

 

Probably, but...

...Not likely.

 

Unity is typically at least one year behind the release of a new specification. C# 8 is only starting to become available with Unity 2020.2.

 

I rather see them move to. NET 5 all together. Mono is a mess. . Net 5 is faster than il2cpp in many cases even

 

Is .Net 5 available for all of Unity's supported platforms?

 

They can keep the mono runtime for crap platforms

 

My guess is they haven't moved off Mono already specifically to avoid the mess of supporting both though.

 

There is a whole thread about that here

 

Using .NET 5 or Mono is the real question

 

Yeah... Mono is a mess. I wonder would there be a massive API change if we migrate from Mono to .NET 5.

 

NET 5 does not support app domains which unity uses to reload when you change code.

 

Is it a Mono-specific feature..?

 

No full framework

 

Or if it is not available in .NET 5, are there any alternatives for Unity to recompile/reload on code changed?

 

.NET Core has collectible assemblies and it seems that .NET 5 has it too:
https://docs.microsoft.com/en-us/do...time_Loader_AssemblyLoadContext_IsCollectible

Collectible assemblies could theoretically improve "Domain reload situation".
Instead of tearing down whole AppDomain and recreating it, it could be possible to just collect Script assemblies and load newer version.

There's a lot of potential problems. First, all references to Script Assemblies and any types and their instances would have to be collected. So Unity would have to destroy and recreate objects (like it's doing now). Some objects might stay alive (like Textures...). Also all references between collected and non-collected assemblies would have to be cleaned up (e.g. subscribed events, objects stored in static fields...).

In worst case, it should be possible to make it same as now (collect all assemblies including UnityEngine, UnityEditor, ... and reload them).

I wonder what is being considered for Unity future, whether Mono is set in stone or whether they're considering .NET Core or .NET 5.

EDIT:
It seems AppDomain removal and AssemblyLoadContext are coming to Mono as well:
https://www.mono-project.com/news/2020/08/24/native-loader-net5/

 

Not gonna lie, I really need that return type covariance.

 

It will make ICloneable and similar use cases so much better

 

Any chance (if it is even at all possible) to just get that C# 9 pattern matching into the current C# 8 inside Unity? Or will I just have to wait till C# 9 support comes along?

 

Please consider NET 5 CLR at the same time, the Mono CLR performance is way behind

 

I love having the features we do have. Thank you for all your hard work! I'm aware of the pain it is to convert a small project from Framework to Core, let alone a much larger project from Mono to Core at a low-level. So again, thank you all so much for even considering it.

 

if c# 9 / .net 5 comes to unity, i think i'm curious the use of record type in unity, along with any other key features in there

 

.NET 6 Preview 1 is out

 

We already have people from Unity, Mono and .NET team on board to "unify" mono, .NET.
It very unlikely Unity gonna leave mono and switch to .Net 5 or CRL anything at all until .NET 6 come out.

Source:
https://devblogs.microsoft.com/dotnet/introducing-net-5/
https://devblogs.microsoft.com/dotnet/announcing-net-6-preview-1/

There is no point of talking when C# 9 or .net 6 coming. Soonest, we will have more info in early 2022 next year.

 

Hi, when c# 9 pattern matching would be added?

Please consider it to at least we beta test it in 2021(non-lt) version

 

Did you read the rest of the thread? They aren't backporting individual C# 9 features. With 2021.2 alpha already available to download, it is way too late to request any major changes like this for the 2021 cycle.

 

So the thing is, C# 9 pattern matching looks like it's there?
What's new in Unity 2021.2.0 Alpha 11 - Unity (unity3d.com)
2021.2.0a11 changelog says they have langversion 9 and a subset of features, including "Pattern matching enhancements." I don't know if that's what you wanted.

 

There is a Visual Studio issue (using VS community 2019 - best free one?) around this in that by default we seem to get suggestions to apply C# 9 formatting shortcuts like the new.. new(); support (Vector3 vec = new(x, y, z) ) which do not compile in 2019 LTS

 

It happened to me after updating both Visual Studio and the Visual Studio Editor extension from UPM. It was fixed after going to Edit → Preferences... → External Tools, and then clicking the "Regenerate project files" button.

 

Any updates?

 

I recommend you check out this thread.