Design: Modernize generated C#

[bricelam]

This is related to #11744, but more general. We should investigate what the minimum version of C# we need to support in EF Core 3.0 is and modernize our generated code. I'm pretty sure there are a few expression bodied methods I'd like add...

[roji]

I think that with #10347 we'd be generating classes that use C# 8 nullability to express requiredness in properties... So I think C# 8 should be fine?

[ajcvickers]

Default is currently "8.0 (beta)"

[ajcvickers]

Consider:

• Reverse engineering to non-nullable types (strings).
• Can we do something based on project configuration?

[roji]

See nullability-related notes here: #10347 (comment)

[bricelam]

I think we can safely assume C# 8.0 as our language minimum version in EF Core 3.0. This is the default for projects targeting .NET Standard 2.1 and .NET Core 3.0.

[bricelam]

Areas I'd like to improve:

• Use nameof in data attributes RevEng: Use nameof in data annotations #11744
• Use auto-property initializers for collection properties
• Use nullable reference types when enabled Migration boilerplate causes "Nullable directive is redundant" if nullable types are disabled #31152
• Consider using AnnotationNames constants (not language-related, but they're public now)

[roji]

There's #15520 for tracking NRT scaffolding, should we close that and track everything there? Note that for NRTs specifically there's the additional opt-in flag so it's an additional thing to do.

[bricelam]

I think it goes beyond DbContext scaffolding too—model snapshots and migrations may also have to be updated when NRT is enabled in the project

[bricelam]

But maybe not as much as I think since NRT is more about member definitions than types...