NPOI大数据分批写入同个Excel

实现过程：
要导出来的数据库数据量很大，一次取出来压力有点大，故分批取出来，导入到同一个Excel。
因为Excel2003版最大行数是65536行，Excel2007开始的版本最大行数是1048576行，故NPOI导出时候选择了Excel2007。

Form1.cs

/*
引用命名空间：
using System.IO;
using System.Threading.Tasks;
using NPOI.HSSF.UserModel;
using NPOI.SS.UserModel;
using NPOI.XSSF.UserModel;
*/
      
public Form1()
{
    InitializeComponent();
    List<DictionaryEntry> list = new List<DictionaryEntry>(){
          new DictionaryEntry(1, "XA"),
          new DictionaryEntry(2, "XB")
    };
    cbType.BindComboBox(list);                    
}

private void CreateExcel(string fileName)
{
    if (File.Exists(fileName))
        File.Delete(fileName);

    IWorkbook workbook = new XSSFWorkbook();
    ISheet sheet = workbook.CreateSheet("Sheet1");
    FileStream sw = File.Create(fileName);
    workbook.Write(sw);
    sw.Close();                   
}


private void btnExport_Click(object sender, EventArgs e)
{            
    try
    {
        Task.Factory.StartNew(() =>
        {
            txtSql.SafeCall(() =>
            {
                txtSql.AppendText("开始处理...
");
            });

            BusinessType businessType = GetBusinessType();
            string[] sqlWhereArray = Sql.SqlWhereArray;
            string[] DateRemarkArray = Sql.DateRemarkArray;
            string fileName = string.Format("{0}.xlsx", businessType.ToString());

            CreateExcel(fileName);                                       

            string sqlCount = Sql.GetRecordSql(businessType, "");
            int recordCount = db.ExecuteScalar(sqlCount);   
            int sqlIndex = 0;
            int rowIndex = 0;
            foreach (string sqlWhre in sqlWhereArray)                    
            {
                sqlIndex++;
                FileStream fs = File.Open(fileName, FileMode.Open);  
                IWorkbook workbook = new XSSFWorkbook(fs);                      
                ISheet sheet = workbook.GetSheetAt(0);
                txtSql.SafeCall(() =>
                {
                    txtSql.AppendText("条件" + sqlIndex.ToString() + "：" + DateRemarkArray[sqlIndex - 1]);
                });
                string sql = Sql.GetDataSql(businessType, sqlWhre);
                DataTable dt = db.GetDataSet(sql).Tables[0];

                int columnsCount = dt.Columns.Count;
                if (sqlIndex == 1)
                {
                    IRow row0 = sheet.CreateRow(0);                            
                    for (int m = 0; m < columnsCount; m++)
                    {
                        DataColumn dc = dt.Columns[m];
                        row0.CreateCell(m).SetCellValue(dc.ColumnName);
                    }
                }

                for (int i = 0; i < dt.Rows.Count; i++)
                {
                    rowIndex++;
                    DataRow dr = dt.Rows[i];                        
                    IRow row = sheet.CreateRow(rowIndex);
                    for (int j = 0; j < columnsCount; j++)
                    {
                        row.CreateCell(j).SetCellValue(dr[j].ToString());
                    }

                    lblMsg.SafeCall(() =>
                    {
                        if(i == (dt.Rows.Count - 1))
                            txtSql.AppendText(" 行数：" + (i+1).ToString() + "
");
                        lblMsg.Text = string.Format("正在导出第{0}个条件，第{1}行", sqlIndex.ToString(), (i + 1).ToString());
                        double x = rowIndex * 1.0 / recordCount * 100;
                        lblProgress.Text = string.Format("总行数：{0}, 当前完成总{1}行，百分占比：{2} %", recordCount.ToString(), rowIndex.ToString(), x.ToString("#0.0"));
                    });
                }
                FileStream outFs = new FileStream(fileName, FileMode.Open);
                workbook.Write(outFs);
                outFs.Close();
            }                   
        }).ContinueWith(TaskEnded);
    }
    catch (Exception ex)
    {
        MessageBox.Show("发生异常，错误提示：" + ex.Message);
    }
}
private void TaskEnded(Task task)
{
    txtSql.SafeCall(() =>
    {
        lblMsg.Text = "全部导出完成！";
        txtSql.AppendText("处理完成！
");               
    });
}

Extensions.cs

public static class Extensions
{
    public static void SafeCall(this Control ctrl, Action callback)
    {
        if (ctrl.InvokeRequired)
            ctrl.Invoke(callback);
        else
            callback();
    }
    public static void BindComboBox(this ComboBox cb, List<DictionaryEntry> list)
    {
        cb.DisplayMember = "Value";
        cb.ValueMember = "Key";
        cb.DataSource = list;
    }
}

Sql.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace DataExport
{
    public enum BusinessType
    {
        XA = 1,
        XB = 2
    }

    public class Sql
    {
        /// <summary>
        /// 分批获取sql的where条件
        /// </summary>
        public static string[] SqlWhereArray = { 
                                 " 条件1 ",
                                 " 条件2 ",
                                 " 条件3 "
                                 };
        
        /// <summary>
        /// sql的where条件说明
        /// </summary>
        public static string[] DateRemarkArray = {  
                            "20130101至20130331",
                            "20130401至20130630",
			    "20130701后",
                             };

        /// <summary>
        /// 获取sql语句
        /// </summary>
        /// <param name="type"></param>
        /// <param name="columns"></param>
        /// <param name="sqlWhere"></param>
        /// <returns></returns>
        private static string GetSql(BusinessType type, string columns, string sqlWhere)
        {
            string sql = "";
            switch (type)
            {
                case BusinessType.XA:
                    sql = string.Format(@"SELECT {0}  FROMM tb1 WHERE 1=1 {1} ", columns, sqlWhere);
                    break;
                case BusinessType.XB:
                    sql = string.Format(@"SELECT {0}  FROMM tb2 WHERE 1=1 {1} ", columns, sqlWhere);
                    break;
            }


            return sql;
        }

        /// <summary>
        /// 获取总记录数
        /// </summary>
        /// <param name="type"></param>
        /// <param name="sqlWhere"></param>
        /// <returns></returns>
        public static string GetRecordSql(BusinessType type, string sqlWhere)
        {
            string columns = "count(*)";
            return GetSql(type, columns, sqlWhere);
        }

        /// <summary>
        /// 获取数据
        /// </summary>
        /// <param name="type"></param>
        /// <param name="sqlWhere"></param>
        /// <returns></returns>
        public static string GetDataSql(BusinessType type, string sqlWhere)
        {
            string columns = "";
            switch (type)
            {
                case BusinessType.XA:
                                columns = @"
                                col1 列1,
				col2 列2,
                                col3 列3
                                 ";
                    break;
                case BusinessType.XB:
                                columns = @"
                                col1 列1,
				col2 列2
                                 ";
                    break;
               
                    }
            return GetSql(type, columns, sqlWhere);
       }
    }
}