Excel操作--使用NPOI导入导出Excel为DataTable

1.ExcelHelper封装

 namespace NPOI操作Excel
 {
     public class ExcelHelper
     {
         /// <summary>
         /// DataTable转成Excel，返回一个文件流
         /// </summary>
         /// <param name="dataTable"></param>
         /// <returns></returns>
         public static Stream DatatableToExcel(DataTable dataTable)
         {
             IWorkbook wk = new HSSFWorkbook();
             MemoryStream ms = new MemoryStream();
             ISheet sheet = wk.CreateSheet();
             IRow headerRow = sheet.CreateRow();

             //处理标题部分
             foreach (DataColumn column in dataTable.Columns)
             {
                 headerRow.CreateCell(column.Ordinal).SetCellValue(column.ColumnName);
             }
             //处理table中的数据
             int rowIndex = ;
             foreach (DataRow row in dataTable.Rows)
             {
                 IRow dataRow = sheet.CreateRow(rowIndex);
                 foreach (DataColumn column in dataTable.Columns)
                 {
                     //column.Ordinal得到从0开始的列的位置，column.ColumnName的到列的名称
                     dataRow.CreateCell(column.Ordinal).SetCellValue(row[column.ColumnName].ToString());
                 }
                 rowIndex++;
             }
             wk.Write(ms);
             ms.Flush();
             ms.Position = ;

             sheet = null;
             headerRow = null;
             return ms;
         }

         /// <summary>
         /// 读取Excel文件,转换成DataTable
         /// </summary>
         /// <param name="ExcelFileStream">读取到Excel的文件流</param>
         /// <param name="SheetIndex">表的索引</param>
         /// <param name="HeaderRowIndex">标题行的索引</param>
         /// <returns></returns>
         public static DataTable DataTableFromExcel(Stream ExcelFileStream, int SheetIndex, int HeaderRowIndex)
         {
             IWorkbook wk = new HSSFWorkbook(ExcelFileStream);
             ISheet sheet = wk.GetSheetAt(SheetIndex);

             DataTable table = new DataTable();

             IRow headerRow = sheet.GetRow(HeaderRowIndex);
             int cellCount = headerRow.LastCellNum;

             //处理标题行的数据
             for (int i = headerRow.FirstCellNum; i < cellCount; i++)
             {
                 DataColumn column = new DataColumn(headerRow.GetCell(i).StringCellValue);
                 table.Columns.Add(column);
             }
             //循环遍历sheet中的每一行，读取每一单元格的数据，同时创建table中的每一行，填充数据
             int rowCount = sheet.LastRowNum;
             for (int i = (sheet.FirstRowNum + ); i <= sheet.LastRowNum; i++)
             {
                 IRow row = sheet.GetRow(i);
                 //以表的格式创建一个新的行
                 DataRow dataRow = table.NewRow();

                 for (int j = row.FirstCellNum; j < cellCount; j++)
                 {
                     if (row.GetCell(j) != null)
                     {
                         dataRow[j] = row.GetCell(j).ToString();
                     }
                 }
                 //dataRow的数据填充好后把行加到表中
                 table.Rows.Add(dataRow);
             }
             ExcelFileStream.Close();
             wk = null;
             sheet = null;
             return table;
         }
     }
 }

2.SqlHelper封装

 namespace NPOI操作Excel
 {
     public static class SqlHelper
     {
         //从配置文件中读取连接字符串
         private static readonly string conStr = ConfigurationManager.ConnectionStrings["conStr"].ConnectionString;
         //执行命令的方法 insert update delete
         public static int ExecuteNonquey(string sql, params SqlParameter[] ps)
         {
             using (SqlConnection con = new SqlConnection(conStr))
             {
                 using (SqlCommand cmd = new SqlCommand(sql, con))
                 {
                     con.Open();
                     cmd.Parameters.AddRange(ps);
                     return cmd.ExecuteNonQuery();
                 }
             }
         }
         //获取首行首列
         public static object ExecuteScalar(string sql, params SqlParameter[] ps)
         {
             using (SqlConnection con = new SqlConnection(conStr))
             {
                 using (SqlCommand cmd = new SqlCommand(sql, con))
                 {
                     con.Open();
                     cmd.Parameters.AddRange(ps);
                     return cmd.ExecuteScalar();
                 }
             }
         }

         //获取读取数据库的对象
         public static SqlDataReader ExecuteDataReader(string sql, params SqlParameter[] ps)
         {
             SqlConnection con = new SqlConnection(conStr);
             using (SqlCommand cmd = new SqlCommand(sql, con))
             {
                 try
                 {
                     con.Open();
                     cmd.Parameters.AddRange(ps);
                     return cmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection);
                 }
                 catch (Exception ex)
                 {
                     con.Close();
                     con.Dispose();
                     throw ex;
                 }
             }
         }
         //获取结果集
         public static DataTable GetDataTable(string sql, params SqlParameter[] ps)
         {
             //构造数据表，用于接收查询结果
             DataTable dt = new DataTable();
             //构造适配器对象
             using (SqlDataAdapter sda = new SqlDataAdapter(sql, conStr))
             {
                 //添加参数
                 sda.SelectCommand.Parameters.AddRange(ps);
                 //执行
                 sda.Fill(dt);
                 return dt;
             }
         }

     }
 }

3.winform中操作

3.1从数据库读取数据导入到Excel中

         private void button1_Click(object sender, EventArgs e)
         {
             DataTable dt = SqlHelper.GetDataTable("select * from t_persons");
             MemoryStream ms = ExcelHelper.DatatableToExcel(dt) as MemoryStream;

             string saveFileNme = "";
             bool fileSaved = false;
             //保存文件对话框
             SaveFileDialog saveDialog = new SaveFileDialog();
             //设置默认的文件类型
             saveDialog.DefaultExt = "xls";
             saveDialog.Filter = "Excel文件|*.xls";
             //设置文件名
             saveDialog.FileName = "保存";
             saveDialog.ShowDialog();
             //获得文件全路径
             saveFileNme = saveDialog.FileName;
             if (saveFileNme.IndexOf(":") < ) return;
             if (saveFileNme != "")
             {
                 try
                 {
                     FileStream fs = new FileStream(saveDialog.FileName, FileMode.Create);
                     fs.Write(ms.GetBuffer(), , ms.GetBuffer().Length);
                     ms.Close();
                     ms.Dispose();
                     fs.Close();
                     fileSaved = true;
                 }
                 catch (Exception ex)
                 {
                     fileSaved = false;
                     MessageBox.Show("导出文件出错，文件可能正在被占用\n" + ex.Message);
                 }
             }
             else
             {
                 fileSaved = false;
             }
             GC.Collect();//强行销毁
             if (fileSaved&&File.Exists(saveFileNme))
             {
                 MessageBox.Show("导出成功", "通知");
             }
             else
             {
                 MessageBox.Show("导出失败", "通知");
             }
         }

3.2读取Excel文件，转换成DataTable绑定到DataGridView上

         private void button2_Click(object sender, EventArgs e)
         {
             //打开文件对话框
             OpenFileDialog fileDialog=new OpenFileDialog();
             //指定要打开文件的格式
             fileDialog.Filter = "Excel文件|*.xls";
             //设置默认打开路径
             fileDialog.InitialDirectory = @"C:\Users\LWP1398\Desktop";
             if (fileDialog.ShowDialog()==DialogResult.OK)
             {
                 string fileName = fileDialog.FileName;//得到文件全路径
                 using (FileStream fsRead=new FileStream(fileName,FileMode.Open,FileAccess.Read))
                 {
                     DataTable dt = ExcelHelper.DataTableFromExcel(fsRead, , );
                     dgv.DataSource = dt;
                 }
             }
             MessageBox.Show("ok");
         }
     }

NPOI目前主要还是操作xls文件，对操作xlsx文件支持得不是很好