C# 使用 Npoi 操作Excel文件，你明白了吗？

C#使用NPOI操作excel
将DataTable数据导入到excel中
 
/// <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(System.Data.DataTable data, string sheetName, bool isColumnWritten)
      {
          int i = 0;
          int j = 0;
          int count = 0;
          ISheet sheet = null;
 
          try
          {
              fs = new FileStream(fileName, FileMode.OpenOrCreate, FileAccess.ReadWrite);
              if (fileName.IndexOf(".xls") > 0) // 2003版本
                  workbook = new HSSFWorkbook();
 
              if (workbook != null)
              {
                  sheet = workbook.CreateSheet(sheetName);
              }
              else
              {
                  return -1;
              }
 
              if (isColumnWritten == true) //写入DataTable的列名
              {
                  IRow row = sheet.CreateRow(0);
                  for (j = 0; j < data.Columns.Count; ++j)
                  {
                      row.CreateCell(j).SetCellValue(data.Columns[j].ColumnName);
                  }
                  count = 1;
              }
              else
              {
                  count = 0;
              }
 
              for (i = 0; i < data.Rows.Count; ++i)
              {
                  IRow row = sheet.CreateRow(count);
                  for (j = 0; 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 -1;
          }
          finally
          {
              fs?.Close();
          }
      }
将excel中的数据导入到DataTable中
 
/// <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 System.Data.DataTable ExcelToDataTable(string sheetName, bool isFirstRowColumn)
      {
          ISheet sheet = null;
          var data = new System.Data.DataTable();
          int startRow = 0;
          try
          {
              fs = new FileStream(fileName, FileMode.Open, FileAccess.Read);
              if (fileName.IndexOf(".xls") > 0) // 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(0);
                  }
              }
              else
              {
                  sheet = workbook.GetSheetAt(0);
              }
              if (sheet != null)
              {
                  IRow firstRow = sheet.GetRow(0);
                  int cellCount = firstRow.LastCellNum; //一行最后一个cell的编号 即总的列数
                  for (int i = 0; i < cellCount; ++i)
                  {
                      var column = new System.Data.DataColumn("column" + i);
                      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)
                  {
                      IRow row = sheet.GetRow(i);
                      if (row == null) continue; //没有数据的行默认是null        
 
                      var 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)
          {
              Console.WriteLine("Exception: " + ex.Message);
              return null;
          }
      }