C#利用NPOI操作Excel文件

　　NPOI作为开源免费的组件，功能强大，可用来读写Excel(兼容xls和xlsx两种版本)、Word、PPT文件。可是要让我们记住所有的操作，这便有点困难了，至此，总结一些在开发中常用的针对Excel的简单。NPOI官网地址

　　本文地址：https://www.cnblogs.com/CKExp/p/9626022.html

一、NPOI的安装

　　下载NPOI或是通过Nuget包加入进来，然后在代码中引用如下命名空间，然后开始读写Excel文件。

using NPOI.SS.UserModel;
using NPOI.XSSF.UserModel;
using NPOI.HSSF.UserModel;
using NPOI.SS.Util;

二、NPOI写入Excel文件

　　在NPOI中，使用HSSFWorkbook类类来处理xls结尾的Excel文件(版本在2003及以前)，XSSFWorkbook类来处理xlsx结尾的Excel文件(版本在2007及以后)，都继承自接口IWorkbook，我们可以使用IWorkbook来统一处理两种不同格式的Excel文件。

　　直接参考相关代码即可，对于合并单元格的跨行跨列操作，无需将被跨掉的行生成新行，合并单元格的信息是单独保存的。设置单元格样式时，请创建一个新的样式对象，不创建将使用默认的样式对象。

 /// <summary>
 /// Datable导出到Excel
 /// </summary>
 /// <returns></returns>
 public static void DataTableToExcel()
 {
     //一些已有数据信息
     bool fileSaved = false;
     SaveFileDialog saveDialog = new SaveFileDialog
     {
         DefaultExt = "xls",
         Filter = "Excel文件|*.xls",
         FileName = DateTime.Now.ToString("yyyyMMdd") + "-" + enterpriseTable.Rows[]["名称"].ToString() + "委托书"
     };
     saveDialog.ShowDialog();
     string saveFileName = saveDialog.FileName;
     if (saveFileName.IndexOf(":") < ) return; //被点了取消
     if (saveFileName != "")
     {
         try
         {
             IWorkbook workbook;
             string fileExt = System.IO.Path.GetExtension(saveFileName).ToLower();
             if (fileExt == ".xlsx")
             {
                 workbook = new XSSFWorkbook();
             }
             else if (fileExt == ".xls")
             {
                 workbook = new HSSFWorkbook();
             }
             else
             {
                 return;
             }

             ISheet sheet = workbook.CreateSheet("Sheet1");

             sheet.AddMergedRegion(new CellRangeAddress(, , , ));//合并单元格
             IRow row = sheet.CreateRow();//创建首行
             ICell cell = row.CreateCell();//行中创建第一列
             cell.SetCellValue("标题");
             ICellStyle style = workbook.CreateCellStyle();//设置样式，创建新的style实例，脱离统一样式
             style.Alignment = NPOI.SS.UserModel.HorizontalAlignment.Center;//设置单元格的样式：水平对齐居中
             style.VerticalAlignment = NPOI.SS.UserModel.VerticalAlignment.Center;

             IFont font = workbook.CreateFont();//新建一个字体样式对象
             font.Boldweight = short.MaxValue; //设置字体加粗样式
             style.SetFont(font); //使用SetFont方法将字体样式添加到单元格样式中
             cell.CellStyle = style; //将新的样式赋给单元格

             sheet.AddMergedRegion(new CellRangeAddress(, , , ));
             sheet.AddMergedRegion(new CellRangeAddress(, , , ));
             row = sheet.CreateRow();
             cell = row.CreateCell();
             cell.SetCellValue("编号:");
             cell = row.CreateCell();
             cell.SetCellValue(planCode);
             cell = row.CreateCell();
             cell.SetCellValue("日期：");
             cell = row.CreateCell();
             cell.SetCellValue(taskPlantable.Rows[]["编制日期"].ToString());

             sheet.AddMergedRegion(new CellRangeAddress(, , , ));
             sheet.AddMergedRegion(new CellRangeAddress(, , , ));
             row = sheet.CreateRow();
             cell = row.CreateCell();
             cell.SetCellValue("单位:");
             cell = row.CreateCell();
             cell.SetCellValue(enterpriseTable.Rows[]["名称"].ToString());
             cell = row.CreateCell();
             cell.SetCellValue("联系人：");
             cell = row.CreateCell();
             cell.SetCellValue(enterpriseTable.Rows[]["联系人"].ToString());

             sheet.AddMergedRegion(new CellRangeAddress(, , , ));
             sheet.AddMergedRegion(new CellRangeAddress(, , , ));
             row = sheet.CreateRow();
             cell = row.CreateCell();
             cell.SetCellValue("传真:");
             cell = row.CreateCell();
             cell.SetCellValue(enterpriseTable.Rows[]["传真"].ToString());
             cell = row.CreateCell();
             cell.SetCellValue("联系电话：");
             cell = row.CreateCell();
             cell.SetCellValue(enterpriseTable.Rows[]["电话"].ToString());

             sheet.AddMergedRegion(new CellRangeAddress(, , , ));
             row = sheet.CreateRow();
             cell = row.CreateCell();
             cell.SetCellValue("详细地址:");
             cell = row.CreateCell();
             cell.SetCellValue(enterpriseTable.Rows[]["详细地址"].ToString());

             int index = ;
             //数据
             for (int i = ; i < taskProjectTable.Rows.Count; i++)
             {
                 index++;
                 sheet.AddMergedRegion(new CellRangeAddress(index, index, , ));
                 sheet.AddMergedRegion(new CellRangeAddress(index, index, , ));
                 row = sheet.CreateRow(index);
                 cell = row.CreateCell();
                 cell.SetCellValue("名称:");
                 cell = row.CreateCell();
                 cell.SetCellValue(taskProjectTable.Rows[i]["名称"].ToString());
                 cell = row.CreateCell();
                 cell.SetCellValue("类型:");
                 cell = row.CreateCell();
                 cell.SetCellValue(taskProjectTable.Rows[i]["项目类型"].ToString());

                 index++;
                 sheet.AddMergedRegion(new CellRangeAddress(index, index, , ));
                 sheet.AddMergedRegion(new CellRangeAddress(index, index, , ));
                 sheet.AddMergedRegion(new CellRangeAddress(index, index, , ));
                 row = sheet.CreateRow(index);
                 cell = row.CreateCell();
                 cell.SetCellValue("项目");
                 cell = row.CreateCell();
                 cell.SetCellValue("方法");
                 cell = row.CreateCell();
                 cell.SetCellValue("仪器");

                 //获取数据信息
                 DataTable taskDataTable = mysql.GetTableFromSQL(selstr.ToString());
                 selstr.Clear();
                 for (int j = ; j < taskDataTable.Rows.Count; j++)
                 {
                     index++;
                     sheet.AddMergedRegion(new CellRangeAddress(index, index, , ));
                     sheet.AddMergedRegion(new CellRangeAddress(index, index, , ));
                     sheet.AddMergedRegion(new CellRangeAddress(index, index, , ));
                     row = sheet.CreateRow(index);
                     cell = row.CreateCell();
                     cell.SetCellValue(taskDataTable.Rows[j]["名称"].ToString());
                     cell = row.CreateCell();
                     cell.SetCellValue(taskDataTable.Rows[j]["方法"].ToString());
                     cell = row.CreateCell();
                     cell.SetCellValue(taskDataTable.Rows[j]["仪器型号"].ToString());
                 }
             }

             //转为字节数组
             MemoryStream stream = new MemoryStream();
             workbook.Write(stream);
             var buf = stream.ToArray();

             //保存为Excel文件
             using (FileStream fs = new FileStream(saveDialog.FileName, FileMode.Create, FileAccess.Write))
             {
                 fs.Write(buf, , buf.Length);
                 fs.Flush();
             }
             fileSaved = true;
         }
         catch (Exception ex)
         {
             fileSaved = false;
             MessageBox.Show("导出文件时出错,文件可能正被打开！\n" + ex.Message);
         }
     }
     GC.Collect();//强行销毁

     if (fileSaved && File.Exists(saveFileName))
     {
         MessageBox.Show("导出成功！", "通知");
         Process.Start(saveFileName);
     }
     else
     {
         MessageBox.Show("导出失败！", "通知");
     }
 }

三、NPOI读取Excel文件

　　打开指定Excel文件并读取文件中的内容，加入到DataTable中，或是加入到其它的数据载体中。

 /// <summary>
 /// Excel导入成DataTble
 /// </summary>
 /// <param name="file">导入路径(包含文件名与扩展名)</param>
 /// <returns></returns>
 public static DataTable ExcelToTable(string file)
 {
     DataTable dt = new DataTable();
     IWorkbook workbook;
     string fileExt = Path.GetExtension(file).ToLower();
     using (FileStream fs = new FileStream(file, FileMode.Open, FileAccess.Read))
     {
         if (fileExt == ".xlsx") { workbook = new XSSFWorkbook(fs); } else if (fileExt == ".xls") { workbook = new HSSFWorkbook(fs); } else { workbook = null; }
         if (workbook == null) { return null; }
         ISheet sheet = workbook.GetSheetAt();

         //表头
         IRow header = sheet.GetRow(sheet.FirstRowNum);
         List<int> columns = new List<int>();
         for (int i = ; i < header.LastCellNum; i++)
         {
             object obj = GetValueType(header.GetCell(i));
             if (obj == null || obj.ToString() == string.Empty)
             {
                 dt.Columns.Add(new DataColumn("Columns" + i.ToString()));
             }
             else
                 dt.Columns.Add(new DataColumn(obj.ToString()));
             columns.Add(i);
         }
         //数据
         for (int i = sheet.FirstRowNum + ; i <= sheet.LastRowNum; i++)
         {
             DataRow dr = dt.NewRow();
             bool hasValue = false;
             foreach (int j in columns)
             {
                 dr[j] = GetValueType(sheet.GetRow(i).GetCell(j));
                 if (dr[j] != null && dr[j].ToString() != string.Empty)
                 {
                     hasValue = true;
                 }
             }
             if (hasValue)
             {
                 dt.Rows.Add(dr);
             }
         }
     }
     return dt;
 }

四、对单元格数据类型的操作

　　获取目标单元格的数据类型及数据值。

 /// <summary>
 /// 获取单元格类型
 /// </summary>
 /// <param name="cell">目标单元格</param>
 /// <returns></returns>
 private static object GetValueType(ICell cell)
 {
     if (cell == null)
         return null;
     switch (cell.CellType)
     {
         case CellType.Blank:
             return null;
         case CellType.Boolean:
             return cell.BooleanCellValue;
         case CellType.Numeric:
             return cell.NumericCellValue;
         case CellType.String:
             return cell.StringCellValue;
         case CellType.Error:
             return cell.ErrorCellValue;
         case CellType.Formula:
         default:
             return "=" + cell.CellFormula;
     }
 }

　　将数据设置到目标单元格中，并设置为指定数据格式。

 /// <summary>
 /// 设置单元格数据类型
 /// </summary>
 /// <param name="cell">目标单元格</param>
 /// <param name="obj">数据值</param>
 /// <returns></returns>
 public static void SetCellValue(ICell cell, object obj)
 {
     if (obj.GetType() == typeof(int))
     {
         cell.SetCellValue((int)obj);
     }
     else if (obj.GetType() == typeof(double))
     {
         cell.SetCellValue((double)obj);
     }
     else if (obj.GetType() == typeof(IRichTextString))
     {
         cell.SetCellValue((IRichTextString)obj);
     }
     else if (obj.GetType() == typeof(string))
     {
         cell.SetCellValue(obj.ToString());
     }
     else if (obj.GetType() == typeof(DateTime))
     {
         cell.SetCellValue((DateTime)obj);
     }
     else if (obj.GetType() == typeof(bool))
     {
         cell.SetCellValue((bool)obj);
     }
     else
     {
         cell.SetCellValue(obj.ToString());
     }
 }

　　本文地址：https://www.cnblogs.com/CKExp/p/9626022.html

2018-09-11,望技术有成后能回来看见自己的脚步