C# 使用NPOI 处理Excel（Datable与Excel相互转换）

VS上有自带的程序集可以读取，但是总是会出现这样或那样的问题，让人恨得牙疼！而且效率太慢了。用NPOI就好多了，比较快，而且稳定，还简单，引用相应的程序集就好了。

Excel转换成Datable

private IWorkbook workbook = null;
        private FileStream fs = null;
        /// <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 fileName, bool isFirstRowColumn=true)
        {
            string sheetName = Path.GetFileName(fileName);
            ISheet sheet = null;
            DataTable data = new DataTable();
            int startRow = ;
            try
            {
                fs = new FileStream(fileName, FileMode.Open, FileAccess.Read);
                if (fileName.IndexOf(".xlsx") > ) // 2007版本
                    workbook = new XSSFWorkbook(fs);
                else if (fileName.IndexOf(".xls") > ) // 2003版本
                    workbook = new HSSFWorkbook(fs);

                if (sheetName != null)
                {
                    sheet = workbook.GetSheet(sheetName);
                    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();
                    }
                }
                else
                {
                    sheet = workbook.GetSheetAt();
                }
                if (sheet != null)
                {
                    IRow firstRow = sheet.GetRow();
                    int cellCount = firstRow.LastCellNum; //一行最后一个cell的编号 即总的列数

                    if (isFirstRowColumn)
                    {
                        for (int i = firstRow.FirstCellNum; i < cellCount; ++i)
                        {
                            ICell cell = firstRow.GetCell(i);
                            if (cell != null)
                            {
                                string cellValue = cell.StringCellValue;
                                if (cellValue != null)
                                {
                                    DataColumn column = new DataColumn(cellValue);
                                    data.Columns.Add(column);
                                }
                            }
                        }
                        startRow = sheet.FirstRowNum + ;
                    }
                    else
                    {
                        startRow = sheet.FirstRowNum;
                    }

                    //最后一列的标号
                    int rowCount = sheet.LastRowNum;
                    for (int i = startRow; i <= rowCount; ++i)
                    {
                        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)
                        {
                            if (row.GetCell(j) != null) //同理，没有数据的单元格都默认是null
                                dataRow[j] = row.GetCell(j).ToString();
                        }
                        data.Rows.Add(dataRow);
                    }
                }

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

Datable转换成Excel

 private string fileName = null; //文件名
         private IWorkbook workbook = null;
         private FileStream fs = null;
         private bool disposed;

         /// <summary>
          /// 将DataTable数据导入到excel中
         /// </summary>
          /// <param name="data">要导入的数据</param>
          /// <param name="isColumnWritten">DataTable的列名是否要导入</param>
         /// <param name="sheetName">要导入的excel的sheet的名称</param>
         /// <returns>导入数据行数(包含列名那一行)</returns>
         public int DataTableToExcel(DataTable data, string sheetName, bool isColumnWritten)
         {
             fileName = @"E:\11.xlsx";
             int i = ;
             int j = ;
             int count = ;
             ISheet sheet = null;

             FileStream fs = new FileStream(fileName, FileMode.OpenOrCreate, FileAccess.ReadWrite);
             if (fileName.IndexOf(".xlsx") > ) // 2007版本
                workbook = new XSSFWorkbook();
             else if (fileName.IndexOf(".xls") > ) // 2003版本
                 workbook = new HSSFWorkbook();

             try
             {
                if (workbook != null)
                 {
                     sheet = workbook.CreateSheet(sheetName);
                 }
                 else
                 {
                     return -;
                 }

                 if (isColumnWritten == true) //写入DataTable的列名
                 {
                     IRow row = sheet.CreateRow();
                     for (j = ; j < data.Columns.Count; ++j)
                     {
                         row.CreateCell(j).SetCellValue(data.Columns[j].ColumnName);
                     }
                     count = ;
                 }
                 else
                 {
                     count = ;
                 }

                 for (i = ; i < data.Rows.Count; ++i)
                 {
                   IRow row = sheet.CreateRow(count);
                     for (j = ; j < data.Columns.Count; ++j)
                     {
                         row.CreateCell(j).SetCellValue(data.Rows[i][j].ToString());
                     }
                     ++count;
                 }
                 workbook.Write(fs); //写入到excel
                 return count;
             }
             catch (Exception ex)
             {
                 Console.WriteLine("Exception: " + ex.Message);
                 return -;
             }
         }

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