Basically, im trying to convert a VehicleDTO, which has some properties, to my Vehicle model, which has a lot of more properties, so when i map it, the unmapped properties are null, and when its time to update it, that causes a couple of errors, like some values that cant be null, or just updates the object but clears the previous values and set them to null.

Im using entity framework

/*AutoMapperProfile.cs*/
CreateMap<VehiculoDTO, Vehiculo>()
.ConvertUsing<MapeoVehiculosDTO_VehiculosTypeConverter>();

/*FuncionesMapeos.cs*/
public class MapeoVehiculosDTO_VehiculosTypeConverter : ITypeConverter<VehiculoDTO, Vehiculo> {
    public Vehiculo Convert(VehiculoDTO source, Vehiculo destination, ResolutionContext context) {
        destination = new();

        if (source is not null) {
            destination.Id = source.Id;
            destination.Matricula = source.Matricula;
            if (source.IdMarca is not null) {
                destination.MarcaId = source.IdMarca;
            }

            if (source.IdModelo is not null) {
                destination.ModeloId = source.IdModelo;
            }

            if (source.Id_TipoCombustible is not null) {
                destination.TipoCombustibleId = source.Id_TipoCombustible;
            }

                destination.IdEmpresa = source.IdEmpresa;
            
        }

        return destination;
    }
}

I tried to use functions like IgnoreAllUnmapped, but i always get the same result.