Linq使用事务

public void AddBook(int userId, acb_Book newBook, bool defaultBook, int startMoney)
{
    using (AccountBookDataContext ctx = new AccountBookDataContext())
    {
        int haveBookCount = ctx.acb_Book.Count(b => b.CreateAccountId == userId);
        if (haveBookCount < 5)
        {
            ctx.Connection.Open();
            ctx.Transaction = ctx.Connection.BeginTransaction(IsolationLevel.Serializable);
            try
            {
                ctx.acb_Book.InsertOnSubmit(newBook);
                ctx.SubmitChanges();

                if (defaultBook)
                {
                    newBook.acb_UserInfo.DefaultBookId = newBook.Id;
                }
                ctx.SubmitChanges();

                if (startMoney != 0)
                {
                    acb_BookItem item = new acb_BookItem();
                    item.AccountDateTime = DateTime.Now;
                    item.CreateAccountId = userId;
                    item.CreaetDateTime = DateTime.Now;
                    item.Name = "我的启动资金";
                    item.Money = startMoney;
                    item.acb_SystemClass = (from sc in ctx.acb_SystemClass where sc.Name == "暂无分类" select sc).Single();
                    newBook.acb_BookItem.Add(item);
                }
                ctx.SubmitChanges();

                ctx.Transaction.Commit();
            }
            catch (Exception ex)
            {
                ctx.Transaction.Rollback();
                throw ex;
            }
            finally
            {
                ctx.Connection.Close();
                ctx.Transaction = null;
            }
        }
        else
        {
            throw new Exception("每个用户只能创建5个帐本");
        }
    }
}