C# 更新集合中某一个信息也是集合的数据

比如一个集合中，还有一个多选项，此多选项是作为一个集合，传输在总的集合上，更新这个多选项集合的代码

1.先更新总集合的基本数据

2.针对这个多选项集合的值，更新多选项

//从DB删除已经删除的问题
                    if (exam.ID > 0)
                    {
                        var sql = string.Empty;
                        if (exam.Questions.Where(o => o.ID > 0).Count() > 0)
                        {
                            sql = string.Format("UPDATE dbo.Question SET IsDeleted = 1 WHERE IsDeleted = 0 AND ExamSn = '{0}' AND ID NOT IN ({1})", exam.Sn, string.Join(",", exam.Questions.Where(o => o.ID > 0).Select(o => o.ID)));
                        }
                        else
                        {
                            sql = string.Format("UPDATE dbo.Question SET IsDeleted = 1 WHERE IsDeleted = 0 AND ExamSn = '{0}'", exam.Sn);
                        }
                        db.ExecuteNonQuerySql(sql);
                    }
                    foreach (var q in exam.Questions)
                    {
                        var q_result = false;
                        if (q.ID == 0)
                        {
                            q.IsDeleted = false;
                            q.Sn = Guid.NewGuid();
                            q.ExamSn = exam.Sn;
                            q_result = service.Create(q);
                        }
                        else
                        {
                            q_result = service.Update(q);
                        }30                     }