Existing target object

If an existing object instance should be used as target, you can define the mapping method as void with the target as second parameter:

Mapper declaration

[Mapper]
public partial class CarMapper
{
    public partial void CarToCarDto(Car car, CarDto dto);
}

Mapper usage

var mapper = new CarMapper();
var car = new Car { NumberOfSeats = 10, ... };
var dto = new CarDto();

mapper.CarToCarDto(car, dto);
dto.NumberOfSeats.Should().Be(10);