Remove `netstandard 2.1` and targeting only .NET 9

[ajara87]

Summary

I would like to propose removing .NET Standard 2.1 from NEO

• .NET Standard is frozen. Microsoft will not release versions beyond 2.1. Link

• .NET 9 brings substantial performance and tooling gains (JIT/PGO, loop/inlining optimizations, faster exceptions) that can't fully leverage while targeting netstandard 2.1

• Simpler builds & maintenance: fewer TFMs mean fewer #ifs, smaller CI matrices and less divergent code paths

The only reason to maintain .NET Standard should be to share code between Mono and .NET Core 3.x (as Microsoft mention link) (Given that .NET Core 3.x is no longer supported by Microsoft and .NET Standard 2.1 not support .NET Framework).

Maybe I'm overlooking a strong reason to keep .NET Standard, but unless that's the case, it could probably be removed at least partially, if not entirely.

[shargon]

If net 9 works in mobile, have no sense to preserve an obsolete framework

[ajara87]

Yes, it's possible to use net9 in mobile. Link

[cschuchardt88]

AOT replaces netstandard we should add that

[ajara87]

I agree we can add AOT

[Wi1l-B0t]

I agree we can add AOT

I have tried adding AOT support.

It's hard to do, but you can give it a try.

[vncoelho]

Perhaps some points like Plugins load with Assembly.Load Assembly.Load may cause some problems

[ajara87]

I think the best approach is to make the change in two phases:

• First, remove .NET Standard
• Second, introduce AOT. When introducing AOT, it will be necessary to carefully analyze which projects actually need it, given that .NET Standard is currently used by:
  • Neo
  • Neo.ConsoleService
  • Neo.Cryptography.BLS12_381
  • Neo.Extensions
  • Neo.IO
  • Neo.Json
  • Neo.VM

[shargon]

I think the best approach is to make the change in two phases:

• First, remove .NET Standard

• Second, introduce AOT. When introducing AOT, it will be necessary to carefully analyze which projects actually need it, given that .NET Standard is currently used by:

  • Neo
  • Neo.ConsoleService
  • Neo.Cryptography.BLS12_381
  • Neo.Extensions
  • Neo.IO
  • Neo.Json
  • Neo.VM

First extensions, json io and vm

[Wi1l-B0t]

Maybe these packages should support the previous LTS version.