NPOI写入大数据到excel中，如何降低使用的内存，解决内存占用过大的问题

Question

SystemManage.q_station_log qStationLogsys = new SystemManage.q_station_log();
//int allcount = qStationLogsys.GetAllCount();
int allcount = 100000;
#region
string filename = "xxxx.xls";
string path = "/exceldata/" + filename;
string FilePathName = HttpContext.Current.Server.MapPath(path);
System.IO.File.Delete(FilePathName);
FileStream Fs = new FileStream(FilePathName, FileMode.Create);
IWorkbook workbook = new HSSFWorkbook();
int sheetindex = 1;
ISheet sheet = workbook.CreateSheet("￈xx" + sheetindex.ToString() + "");
int pagesize = 1000;
int currentIndex = 1;
int sheetcount = 0;
#endregion
int fornum = (allcount - allcount % pagesize) / pagesize + 1;
while (currentIndex <= fornum)
{
DataSet ds = qStationLogsys.GetAllLogPart(pagesize, currentIndex);
if (ds.Tables[0].Rows.Count > 0)
{
for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
{
if (sheetcount % 65535 == 0)
{
if (sheetindex != 1)
{
workbook.Write(Fs);
//workbook.Clear();
Fs.Flush();
Fs.Close();
Fs.Dispose();
Fs = new FileStream(FilePathName, FileMode.Open);
sheetcount = 0;
sheet = workbook.CreateSheet("￈xxx" + sheetindex.ToString() + "");

                        }
                        creat_title(sheet);//写入头的内容
                        sheetcount++;
                        sheetindex++;
                        creat_content(sheet, sheetcount, ds.Tables[0].Rows[i]);

//写入内容
}
else
{
creat_content(sheet, sheetcount, ds.Tables[0].Rows[i]);
sheetcount++;
}

                }
            }
            currentIndex++;
            ds.Clear();
        }

        workbook.Write(Fs);
        workbook.Clear();
        Fs.Flush();
        Fs.Close();
        Fs.Dispose();

//-------------------------------------------------
说明：代码如上，实现写入100000条数据，每次从数据库读取1000条，循环写入，当数据超过65535时，会新建一个工作簿。功能已经实现，但是每次写入内容占用过高，有什么方法可以改进，请教下，感激。。。。。