Try .NET/EF 9 RC2

[bkoelman]

Explores multi-targeting against .NET 9 with EF Core 9 pre-release versions. This PR is experimental and not intended to be merged.

Blocked by:

• EF Core 9 support PomeloFoundation/Pomelo.EntityFrameworkCore.MySql#1841
• Regression in .NET 9 RC2: NU1605 Downgrade error which isn't a downgrade NuGet/Home#13855
• Split query with AsNoTrackingWithIdentityResolution() throws ArgumentOutOfRangeException dotnet/efcore#34728
• https://youtrack.jetbrains.com/issue/RSRP-498478/Breaking-primary-constructors-with-readonly-field
• NullReferenceException from CSharpPreferGenericOverloadsAnalyzer in .NET 9 RC1 dotnet/roslyn-analyzers#7421

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 90.79%. Comparing base (eb2ef95) to head (8b76268).

Files with missing lines	Patch %	Lines
src/Examples/DapperExample/Program.cs	0.00%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1550   +/-   ##
=======================================
  Coverage   90.79%   90.79%           
=======================================
  Files         349      349           
  Lines       11314    11315    +1     
  Branches     1849     1849           
=======================================
+ Hits        10272    10274    +2     
- Misses        682      683    +1     
+ Partials      360      358    -2     

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[wayne-o]

Hi - is there a preview Nuget of this anywhere we can try against our own code?

[bkoelman]

I don't think there's a need for that. EF Core 9 targets .NET 8, so the current JADNC version should work already with EF Core 9 on both .NET 8 and 9.

[bkoelman]

I've created #1619 to verify all tests are green when running on .NET 9 RC2 with EF Core 9 RC2, while still referencing JADNC that targets only .NET 8 and 6.

While there are breaking changes in the EF Core driver API (so you'll need matching versions for PostgreSQL, MySQL, SQL Server, etc.), it appears that JADNC itself is already compatible. This means we don't need to release a new version of JADNC when .NET 9 ships.