Copy Attributes

When CopyAttributes = true, Facette copies data annotation and validation attributes from source properties to the generated DTO properties.

Usage

public class Employee
{
    [Required]
    [StringLength(100)]
    public string FirstName { get; set; } = "";

    [EmailAddress]
    public string Email { get; set; } = "";
}

[Facette(typeof(Employee), "SocialSecurityNumber",
    CopyAttributes = true)]
public partial record EmployeeDto;

The generated DTO will include the same attributes:

public partial record EmployeeDto
{
    [Required]
    [StringLength(100)]
    public string FirstName { get; init; }

    [EmailAddress]
    public string Email { get; init; }
}

This is useful for API validation — your DTOs automatically inherit the validation rules defined on your domain models.

Verifying at runtime

var attrs = typeof(EmployeeDto).GetProperty("FirstName")!
    .GetCustomAttributes(false);
// Contains: RequiredAttribute, StringLengthAttribute

Skipped attributes

Some attributes cannot be fully reconstructed at compile time (e.g., attributes with complex constructor arguments or non-constant property values). When Facette encounters these, it skips them and emits FCT012 as an informational diagnostic.

Attributes from certain system namespaces (like System.Runtime.CompilerServices) are also excluded to avoid noise.

When to use

• API DTOs — share validation attributes between model and DTO without duplication
• Swagger/OpenAPI — copied attributes are picked up by schema generators
• FluentValidation interop — if your validators inspect data annotations

When not to use

If your DTO validation rules differ from your domain model, keep CopyAttributes = false (the default) and define attributes manually on the DTO.