这里的代码 比较像聚合 和不是组合？？？

聚合

public class Student {
    ...
};

public class Class {
    private Student _student;  //成员变量
    public Class(Student student) {
        _student = student
    }
};

组合

public class Heart {
    ...
};

public class Student {
    private StudeHeartnt _heart;  //成员变量
    public Student() {
        _heart = new Heart（）;
    }
};

数据迁移

class DbMigrator
{
	private readonly Logger _logger;
	public DbMigrator(Logger logger)
	{
		_logger = logger;
	}
}