Not create but update entity

[IAmAnatolyBelanov]

Is it possible to update fields in existing entity? Something like that:

public class User {...}
public class UserDto {...}

[Mapper]
public partial class Mapper
{
    public partial void FromDto(User user, UserDto dto);
}

// autogenerated
public partial class Mapper
{
    public partial void FromDto(User user, UserDto dto)
    {
        // not create User

        user.Something = dto.Something;
        // other fields

        return user;
    }
}

And then use it like:

public void UpdateUser(UserDto dto)
{
    var user = db.Users.Find(dto.id);
    Mapper.FromDto(user, dto);
    db.SaveChanges();
}

[IAmAnatolyBelanov]

Oh... i just tried to do it, and it works... fell stupid =)