本文实例为大家分享了C#用NPOI导出导入Excel帮助类的具体代码，供大家参考，具体内容如下
1、准备工作
在管理NuGet程序包中搜索 NPOI，安装 NPOI 到要项目中。
2、帮助类
////// DataTable写入Excel /// /// /// ///public bool GridToExcelByNPOI(DataTable dt, string strExcelFileName) { try { HSSFWorkbook workbook = new HSSFWorkbook(); ISheet sheet = workbook.CreateSheet("Sheet1"); ICellStyle HeadercellStyle = workbook.CreateCellStyle(); HeadercellStyle.BorderBottom = NPOI.SS.UserModel.BorderStyle.Thin; HeadercellStyle.BorderLeft = NPOI.SS.UserModel.BorderStyle.Thin; HeadercellStyle.BorderRight = NPOI.SS.UserModel.BorderStyle.Thin; HeadercellStyle.BorderTop = NPOI.SS.UserModel.BorderStyle.Thin; HeadercellStyle.Alignment = NPOI.SS.UserModel.HorizontalAlignment.Center; //字体 NPOI.SS.UserModel.IFont headerfont = workbook.CreateFont(); headerfont.Boldweight = (short)FontBoldWeight.Bold; HeadercellStyle.SetFont(headerfont); //用column name 作为列名 int icolIndex = 0; IRow headerRow = sheet.CreateRow(0); foreach (DataColumn item in dt.Columns) { ICell cell = headerRow.CreateCell(icolIndex); cell.SetCellValue(item.ColumnName); cell.CellStyle = HeadercellStyle; icolIndex++; } ICellStyle cellStyle = workbook.CreateCellStyle(); //为避免日期格式被Excel自动替换，所以设定 format 为 『@』 表示一率当成text來看 cellStyle.DataFormat = HSSFDataFormat.GetBuiltinFormat("@"); cellStyle.BorderBottom = NPOI.SS.UserModel.BorderStyle.Thin; cellStyle.BorderLeft = NPOI.SS.UserModel.BorderStyle.Thin; cellStyle.BorderRight = NPOI.SS.UserModel.BorderStyle.Thin; cellStyle.BorderTop = NPOI.SS.UserModel.BorderStyle.Thin; NPOI.SS.UserModel.IFont cellfont = workbook.CreateFont(); cellfont.Boldweight = (short)FontBoldWeight.Normal; cellStyle.SetFont(cellfont); //建立内容行 int iRowIndex = 1; int iCellIndex = 0; foreach (DataRow Rowitem in dt.Rows) { IRow DataRow = sheet.CreateRow(iRowIndex); foreach (DataColumn Colitem in dt.Columns) { ICell cell = DataRow.CreateCell(iCellIndex); cell.SetCellValue(Rowitem[Colitem].ToString()); cell.CellStyle = cellStyle; iCellIndex++; } iCellIndex = 0; iRowIndex++; } //自适应列宽度 for (int i = 0; i < icolIndex; i++) { sheet.AutoSizeColumn(i); } //写Excel FileStream file = new FileStream(strExcelFileName, FileMode.OpenOrCreate); workbook.Write(file); file.Flush(); file.Close(); return true; } catch (Exception ex) { return false; } } /// /// 将excel中的数据导入到DataTable中 /// /// fileName /// excel工作薄sheet的名称 /// 第一行是否是DataTable的列名 ///返回的DataTable public DataTable ExcelToDataTable(string fileName, string sheetName, bool isFirstRowColumn) { ISheet sheet = null; DataTable data = new DataTable(); IWorkbook workbook = null; FileStream fs = null; int startRow = 0; try { fs = new FileStream(fileName, FileMode.Open, FileAccess.Read); 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); 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 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 + 1; } 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) { Console.WriteLine("Exception: " + ex.Message); return null; } }
3、使用
（1）DataTable写入Excel
var Sql = "select id,name from test";
var dt = DB.DB.ExecuteDataTable(Sql);
//保存文件
string saveName = "temp_" + DateTime.Now.ToString("yyyyMMddHHmmss") + ".xls";
string DownloadExcelDic = "DownloadExcel";
string webDic = AppDomain.CurrentDomain.BaseDirectory + DownloadExcelDic;
if (!Directory.Exists(webDic))//判断目录是否存在
{
Directory.CreateDirectory(webDic);//不存在则创建新目录
}
string path = webDic + @"\" + saveName; //目录+文件名+后缀名
bool isBuild = GridToExcelByNPOI(dt, path);
（2）导入Excel返回DataTable
//1、先上传文件，将文件保存到服务器上 //2、导入Excel string fileDic = "";//文件路径 var dt = ExcelToDataTable(fileDic, "sheet1", true);
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。