循环取数问题，得不到最大的数字

向DataTable guestneeds中加数据               
从给定的needid开始循环，0 <= needid <= 999。
其中0 《= neeid < 900是区间一，900 <= neeid <=999是区间二。
如果给的needid >= 900，循环中递增到超过999，则查区间一是否可加入数据（即区间现有数字是否小于900）有则加，没有则停止加入数据。
其它部分正常，可是得不到needid=999的那一项。请高手指教下，到底是哪时出问题了呢？               //循环开始
                string[] arr = str.Split('\n');
                foreach (string s in arr)
                {
                    s.Trim();
                    if (needid == -1)//如果已经累加过一次，则什么也不做
                    {
                    }
                    else if (needid < 900)
                    {                                    DataRow newRow;
                                    newRow = guestneeds.NewRow();
                                    needtxt = s;
                                    DataRow[] foundRows;
                                    foundRows = guestneeds.Select("needs ='" + needtxt + "'");
                                    if (foundRows.Length == 0)//如果为新要求
                                    {
                                        newRow["needcode"] = needid.ToString();
                                        guestneeds.Rows.Add(newRow);
                                        guestneeds.AcceptChanges();
                                        needcod = needcod + needid.ToString();
                                    }                                
                        needid++;
                    }                    else //如果needid >= 900
                    {
                        if (needid > 999)//如果needid > 999,查小于900 needid的最小序号
                        {
                            DataRow[] foundCode;
                            foundCode = guestneeds.Select("needcode < 900", "needcode DESC");
                            needid = str2int(foundCode[0]["needcode"].ToString()) + 1;//此处应为查找到的小于990的最大needid
                            if (needid < 900)//如果查到的最小序号小于899
                            {
                                            DataRow newRow;
                                            newRow = guestneeds.NewRow();
                                            needtxt = s;
                                            DataRow[] foundRows;
                                            foundRows = guestneeds.Select("needs ='" + needtxt + "'");
                                            if (foundRows.Length == 0)//如果为新要求
                                            {
                                                newRow["needcode"] = needid.ToString();
                                                guestneeds.Rows.Add(newRow);
                                                guestneeds.AcceptChanges();
                                                needcod = needcod + needid.ToString();
                                            }
                                         needid++;                               
                            }
                            else//如果查到的needie=899，录入数据已超过999个
                            {
                                needid = -1;//停止数据加入
                            }
                        }
                        else//如果900 <= needid <= 999
                        {
                                        DataRow newRow;
                                        newRow = guestneeds.NewRow();
                                        needtxt = s;
                                        DataRow[] foundRows;
                                        foundRows = guestneeds.Select("needs ='" + needtxt + "'");
                                        if (foundRows.Length == 0)//如果为新要求
                                        {
                                            newRow["needcode"] = needid.ToString();
                                            guestneeds.Rows.Add(newRow);
                                            guestneeds.AcceptChanges();
                                            needcod = needcod + needid.ToString();
                                        }
                            needid++;
                        }
                    }
                }