Guid conversion

A .NET Guid and a SQL column declaration are different contracts. Arc’s Guid conversion changes the value sent to SQLite; it does not tune indexes, collations, or every EF provider.

Model conversion

BaseDbContext calls ApplyGuidConversion for relevant model types. For manual configuration, this is an OnModelCreating fragment with Cratis.Arc.EntityFrameworkCore and Microsoft.EntityFrameworkCore imported:

modelBuilder.Entity<Customer>()
    .Property(customer => customer.Id)
    .AsGuid(Database.GetDatabaseType());

Here Customer.Id is a Guid property and Database belongs to the context.

Database	What AsGuid(databaseType) adds
SQLite	A Guid → string converter using ToString("D"), with Guid.Parse on reads
PostgreSQL	No additional conversion for a plain Guid; the EF provider supplies its mapping
SQL Server	No additional conversion for a plain Guid; the EF provider supplies its mapping

For a Guid-backed concept, AsGuid delegates to AsConcept. SQLite uses string storage for that converter too. Ordinary ConceptAs<Guid> identifiers remain valid in standalone Arc applications.

Migration declarations

GuidColumn and AddGuidColumn select these SQL type names independently of the model converter:

PostgreSQL	SQL Server	SQLite
UUID	UNIQUEIDENTIFIER	BLOB

The SQLite migration helper therefore declares BLOB even though AsGuid supplies strings. Do not interpret the helper as a CHAR(36) declaration or as binary serialization. Review generated migrations and test existing-data compatibility before changing a schema or representation.

Arc’s built-in database detection covers the three providers above. Other EF providers may have their own Guid support, but Arc does not supply MySQL/Oracle optimization or collation guarantees.

See common column types and concept conversion for related contracts.