NOPI Excel 读取公式生成后的数据

using NPOI.HSSF.UserModel;
using NPOI.SS.UserModel;
using NPOI.XSSF.UserModel;
using System;
using System.Collections.Generic;
using System.Data;
using System.IO;
using System.Linq;
using System.Web;

namespace PortalPBIRS.Models
{
    class ExcelHelper : IDisposable
    {
        private string fileName = null; //文件名
        private IWorkbook workbook = null;
        private FileStream fs = null;
        private bool disposed;
        readonly int EXCEL03_MaxRow = 65535;
        public ExcelHelper(string fileName)
        {
            this.fileName = fileName;
            disposed = false;
        }

        /// <summary>
        /// 将excel中的数据导入到DataTable中
        /// </summary>
        /// <param name="sheetName">excel工作薄sheet的名称</param>
        /// <param name="isFirstRowColumn">第一行是否是DataTable的列名</param>
        /// <returns>返回的DataTable</returns>
        public DataTable ExcelToDataTable(string sheetName, bool isFirstRowColumn)
        {
            ISheet sheet = null;
            DataTable data = new DataTable();
            int startRow = 0;
            try
            {
                fs = new FileStream(fileName, FileMode.Open, FileAccess.Read);//读取文件
                if (fileName.IndexOf(".xlsx") > 0) // 2007版本
                    workbook = new XSSFWorkbook(fs);
                else if (fileName.IndexOf(".xls") > 0) // 2003版本
                    workbook = new HSSFWorkbook(fs);

                if (sheetName != null)
                {
                    sheet = workbook.GetSheet(sheetName);//获取文件的分页
                    if (sheet == null) //如果没有找到指定的sheetName对应的sheet，则尝试获取第一个sheet
                    {
                        sheet = workbook.GetSheetAt(0);
                    }
                }
                else
                {
                    sheet = workbook.GetSheetAt(0);
                }
                if (sheet != null)
                {
                    int k = 0, cellCount = 0;
                    IRow firstRow = sheet.GetRow(0);//获取第一行
                    while (firstRow == null)
                    {
                        firstRow = sheet.GetRow(++k);//排除空行，找到第一个有字符的行
                    }


                    if (isFirstRowColumn)//第一行是列名
                    {
                        cellCount = firstRow.LastCellNum; //一行最后一个cell的编号 即总的列数

                        for (int i = firstRow.FirstCellNum; i < cellCount; ++i)
                        {
                            ICell cell = firstRow.GetCell(i);
                    
                            if (cell != null)
                            {
                                string cellValue = "";
                                if (cell.CellType == CellType.Formula)
                                {
                                    cellValue = cell.RichStringCellValue.String;
                                }
                                else
                                {
                                    cellValue = cell.StringCellValue;
                                }
                     
                                if (cellValue != null)
                                {
                                    DataColumn column = new DataColumn(cellValue.Replace("\n",""));
                                    data.Columns.Add(column);
                                }
                            }
                        }
                        startRow = sheet.FirstRowNum + 1;
                    }
                    else// 第一行不是列名
                    {
                        int max = 0;
                        for (int i = sheet.FirstRowNum; i <= sheet.LastRowNum; i++)// 找到所有行中最多字符
                        {
                            if (sheet.GetRow(i) == null)
                                continue;

                            max = (sheet.GetRow(i).LastCellNum > max) ? sheet.GetRow(i).LastCellNum : max;
                        }
                        cellCount = max;
                        for (int i = firstRow.FirstCellNum; i < cellCount; ++i)
                        {
                            DataColumn column = new DataColumn();
                            data.Columns.Add(column);
                        }
                        startRow = sheet.FirstRowNum;
                    }

                    //最后一列的标号
                    int rowCount = sheet.LastRowNum;

                    for (int i = startRow; i <= rowCount; ++i)//将从文件中获取的数据存储到DataTable中
                    {
                        IRow row = sheet.GetRow(i);

                        if (row == null)
                        {
                            continue; //没有数据的行默认是null
                        }

                        DataRow dataRow = data.NewRow();
                        for (int j = row.FirstCellNum; j < cellCount; ++j)
                        {
                            //同理，没有数据的单元格都默认是null
                            if (row.GetCell(j) != null)
                            {
                                if (row.GetCell(j).CellType == CellType.Formula)
                                {
                                    row.GetCell(j).SetCellType(CellType.String);

                                    dataRow[j]= row.GetCell(j).RichStringCellValue.String;
                                }
                                else
                                {
                                    dataRow[j] = row.GetCell(j).ToString();
                                }
                            }
                        }

                        data.Rows.Add(dataRow);
                    }
                }

                return data;
            }
            catch (Exception ex)
            {
                Console.WriteLine("Exception: " + ex.Message);
                return null;
            }
        }

        /// <summary>
        /// 将DataTable转换为excel2003格式。
        /// </summary>
        /// <param name="dt"></param>
        /// <returns></returns>
        public byte[] DataTableToExcel(DataTable dt, string sheetName)
        {

            IWorkbook book = new HSSFWorkbook();
            if (dt.Rows.Count < EXCEL03_MaxRow)
                DataWrite2Sheet(dt, 0, dt.Rows.Count - 1, book, sheetName);
            else
            {
                int page = dt.Rows.Count / EXCEL03_MaxRow;
                for (int i = 0; i < page; i++)
                {
                    int start = i * EXCEL03_MaxRow;
                    int end = (i * EXCEL03_MaxRow) + EXCEL03_MaxRow - 1;
                    DataWrite2Sheet(dt, start, end, book, sheetName + i.ToString());
                }
                int lastPageItemCount = dt.Rows.Count % EXCEL03_MaxRow;
                DataWrite2Sheet(dt, dt.Rows.Count - lastPageItemCount, lastPageItemCount, book, sheetName + page.ToString());
            }
            MemoryStream ms = new MemoryStream();
            book.Write(ms);
            return ms.ToArray();
        }
        private void DataWrite2Sheet(DataTable dt, int startRow, int endRow, IWorkbook book, string sheetName)
        {
            ISheet sheet = book.CreateSheet(sheetName);
            IRow header = sheet.CreateRow(0);
            for (int i = 0; i < dt.Columns.Count; i++)
            {
                ICell cell = header.CreateCell(i);
                string val = dt.Columns[i].Caption ?? dt.Columns[i].ColumnName;
                cell.SetCellValue(val);
            }
            int rowIndex = 1;
            for (int i = startRow; i <= endRow; i++)
            {
                DataRow dtRow = dt.Rows[i];
                IRow excelRow = sheet.CreateRow(rowIndex++);
                for (int j = 0; j < dtRow.ItemArray.Length; j++)
                {
                    excelRow.CreateCell(j).SetCellValue(dtRow[j].ToString());
                }
            }

        }
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        protected virtual void Dispose(bool disposing)
        {
            if (!this.disposed)
            {
                if (disposing)
                {
                    if (fs != null)
                        fs.Close();
                }

                fs = null;
                disposed = true;
            }
        }

    }
}