CAERIUS005 — Unmapped CLR type falls back to sql_variant

Severity: Warning Category: CaeriusNet.Generator Applies to: [GenerateDto], [GenerateTvp]

Cause

A parameter on a [GenerateDto] or [GenerateTvp] type uses a CLR type that the generator cannot map to a native SQL Server data type. The generated code falls back to SqlDbType.Variant (sql_variant).

Common offenders: System.Uri, System.Version, custom value objects, System.Net.IPAddress, arbitrary reference types, etc.

Why it matters

sql_variant works, but it disables several SQL Server features:

• No participation in indexes (no seek/scan optimizations).
• Cannot back computed columns.
• Cannot be referenced from CHECK constraints.
• Forces boxing/unboxing on every round-trip.
• ORM/tooling support is limited.

How to fix

Replace the offending property with a natively-mapped CLR type, or expose a conversion at the DTO/TVP boundary:

// Before — emits sql_variant.
[GenerateDto]
public sealed partial record EndpointDto(int Id, System.Uri Endpoint);

// After — explicit string mapping; SQL nvarchar works with all features.
[GenerateDto]
public sealed partial record EndpointDto(int Id, string Endpoint);

If you intentionally want sql_variant, suppress the warning with #pragma warning disable CAERIUS005 around the declaration.

See also

• Compiler Diagnostics
• Table-Valued Parameters