Flattening

Flattening lets you pull nested properties up to the top level of your DTO, avoiding deeply nested objects for simple read scenarios.

Convention flattening

Name a DTO property by concatenating the navigation path, and Facette will automatically resolve it:

public class Employee
{
    public Address? HomeAddress { get; set; }
}

public class Address
{
    public string City { get; set; } = "";
    public string State { get; set; } = "";
}

[Facette(typeof(Employee),
    Include = new[] { "Id", "FirstName", "LastName", "HomeAddress" },
    NestedDtos = new[] { typeof(AddressDto) })]
public partial record EmployeeSummaryDto
{
    public string HomeAddressCity { get; init; } = "";
}

HomeAddressCity is automatically resolved as HomeAddress.City because the property name starts with HomeAddress (a navigation property) followed by City (a property on Address).

The generated code:

• FromSource: HomeAddressCity = source.HomeAddress?.City ?? default
• Projection: HomeAddressCity = source.HomeAddress.City

Explicit dot-notation with MapFrom

For non-conventional names or deeper paths, use [MapFrom] with dot notation:

[MapFrom("HomeAddress.State")]
public string State { get; init; } = "";

This maps State on the DTO from HomeAddress.State on the source. The property name doesn't need to follow any convention.

Reverse flattening in ToSource

When generating ToSource(), Facette reverses flattened properties back into their nested structure:

// Generated ToSource handles nested assignment:
var result = new Employee
{
    HomeAddress = new Address
    {
        City = this.HomeAddressCity,
        State = this.State
    }
};

Limitations

• Convention flattening only activates for multi-segment paths (at least two parts: a navigation property and a leaf property). Single-segment names are never treated as flattened paths.
• If a path segment doesn't resolve, Facette emits FCT007.