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...\r\n");
                });  

                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() + "\r\n");
                            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！\r\n");
        });
    }

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);
           }
        }
    }