Clean Architecture sample

Shows EntityLengthsOutputPath: the EF configurations live in the Infrastructure layer, but the generated constants end up in the Domain layer, which does not reference Infrastructure.

MyApp.Domain            no EF Core, no generator, no Infrastructure reference
├── Entities/           plain POCOs (Customer, Order)
├── Validation/         uses EntityLengths.Customer.NameLength
└── Generated/          <- EntityLengths.cs is written here and committed

MyApp.Infrastructure    references Domain + EF Core + the generator
└── Persistence/        AppDbContext and IEntityTypeConfiguration<T> classes (the lengths)

MyApp.Api               composition root, references Domain + Infrastructure

The relevant part of MyApp.Infrastructure.csproj:

<PropertyGroup>
    <EntityLengthsOutputPath>../MyApp.Domain/Generated/EntityLengths.cs</EntityLengthsOutputPath>
    <EntityLengthsOutputNamespace>MyApp.Domain</EntityLengthsOutputNamespace>
</PropertyGroup>

Because an output path is set, the generator does not add the constants to MyApp.Infrastructure as well - otherwise MyApp.Domain.EntityLengths would exist in two assemblies. Infrastructure sees them through its Domain reference.

Running it

dotnet run --project samples/CleanArchitecture/MyApp.Api --framework net9.0

Output:

Customer.Name      max 100
Customer.Email     max 256
Customer.Notes     max 2000
Order.Reference    max 32
Order.ShippingAddr max 400
invalid: Name must be 1 to 100 characters.

Changing a length

Edit CustomerConfiguration.Configure, for example HasMaxLength(100) to HasMaxLength(120), then build twice:

1. The first build writes the new Generated/EntityLengths.cs while Infrastructure compiles - too late for the Domain compilation that already ran in the same build.
2. The second build compiles Domain against the new value.

That is why the file is committed: a clean clone builds in one pass, and a length change shows up in a reviewable diff. Treat it as checked-in generated code and never edit it by hand.

Multi-targeting

All three projects build for net8.0, net9.0 and net10.0 (see $(SupportedTargetFrameworks) in Directory.Build.props), with the EF Core version following the target framework. The inner builds run in parallel and all write the same constants file; the generator only rewrites it when the content actually changes.