项目需要引用NPOI的Nuget包：DotNetCore.NPOI-v1.2.2
A-前端触发下载Excel的方法有三种：
1-JS-Url跳转请求-后台需要返回文件流数据：
window.Location.href = "/ajax/toolhelper.js?action=reBuyExport&beginTime=" + beginTime + "&endTime=" + endTime;
2-使用form+iframe请求文件流-后台需要返回文件流数据：
<form target="downLoadIframe" method="post" action="/ajax/toolhelper.js?action=reBuyExport"> <div class="form-group"> <label for="datetime">beginTime:</label> <input type="date" class="form-control" name="beginTime" placeholder="Enter beginTime" /> </div> <div class="form-group"> <label for="datetime">endTime:</label> <input type="date" class="form-control" name="endTime" placeholder="Enter endTime"> </div> <button type="submit" class="btn btn-primary" id="btnExport">导出Excel</button> </form> <iframe id="downLoadIframe" name="downLoadIframe" style="display:none;"></iframe>
3-JS-Fetch请求使用Blob保存二进制文件流数据，通过A标签下载流文件-后台需要返回文件流数据：
领导推荐这种方法，经过检验的，可以应对大文件下载的超时问题
fetch(url).then(function (res) { res.blob().then(function (blob) { var a = document.createElement('a'); var url = window.URL.createObjectURL(blob); a.href = url; a.download = fileName; a.click(); window.URL.revokeObjectURL(url); }); });
B-后台返回流数据：
Core下的Excel帮助类
/// <summary> /// EXCEL帮助类 /// </summary> /// <typeparam name="T">泛型类</typeparam> /// <typeparam name="TCollection">泛型类集合</typeparam> public class ExcelHelp<T, TCollection> where TCollection : List<T> where T : new() { public static ExcelHelp<T, TCollection> INSTANCE = new ExcelHelp<T, TCollection>(); //获取httpResponse对象原位置，放在这里不知道会报错：服务器无法在发送 HTTP 标头之后追加标头 //可能是这里拿到的httpResponse对象不是最新请求的对象导致的，将其放到方法内部即可 //HttpResponse baseResponse = HttpContext.Current.Response; /// <summary> /// 将数据导出EXCEL /// </summary> /// <param name="tList">要导出的数据集</param> /// <param name="fieldNameAndShowNameDic">键值对集合（键：字段名，值：显示名称）</param> /// <param name="httpResponse">响应</param> /// <param name="excelName">文件名（必须是英文或数字）</param> /// <returns></returns> public async Task ExportExcelData(TCollection tList, Dictionary<string, string> fieldNameAndShowNameDic, HttpResponse httpResponse, string excelName = "exportResult") { IWorkbook workbook = new HSSFWorkbook(); ISheet worksheet = workbook.CreateSheet("sheet1"); List<string> columnNameList = fieldNameAndShowNameDic.Values.ToList(); //设置首列显示 IRow row1 = worksheet.CreateRow(0); ICell cell = null; ICellStyle cellHeadStyle = workbook.CreateCellStyle(); //设置首行字体加粗 IFont font = workbook.CreateFont(); font.Boldweight = short.MaxValue; cellHeadStyle.SetFont(font); for (var i = 0; i < columnNameList.Count; i++) { cell = row1.CreateCell(i); cell.SetCellValue(columnNameList[i]); cell.CellStyle = cellHeadStyle; } //根据反射创建其他行数据 var raws = tList.Count; Dictionary<int, PropertyInfo> indexPropertyDic = this.GetIndexPropertyDic(fieldNameAndShowNameDic.Keys.ToList()); for (int i = 0; i < raws; i++) { row1 = worksheet.CreateRow(i + 1); for (int j = 0; j < fieldNameAndShowNameDic.Count; j++) { cell = row1.CreateCell(j); if (indexPropertyDic[j].PropertyType == typeof(int) || indexPropertyDic[j].PropertyType == typeof(decimal) || indexPropertyDic[j].PropertyType == typeof(double)) { cell.SetCellValue(Convert.ToDouble(indexPropertyDic[j].GetValue(tList[i]))); } else if (indexPropertyDic[j].PropertyType == typeof(DateTime)) { cell.SetCellValue(Convert.ToDateTime(indexPropertyDic[j].GetValue(tList[i]).ToString())); } else if (indexPropertyDic[j].PropertyType == typeof(bool)) { cell.SetCellValue(Convert.ToBoolean(indexPropertyDic[j].GetValue(tList[i]).ToString())); } else { cell.SetCellValue(indexPropertyDic[j].GetValue(tList[i]).ToString()); } } //设置行宽度自适应 worksheet.AutoSizeColumn(i, true); } //对于.xls文件 //application/vnd.ms-excel //用于.xlsx文件。 //application/vnd.openxmlformats-officedocument.spreadsheetml.sheet MediaTypeHeaderValue mediaType = new MediaTypeHeaderValue("application/vnd.ms-excel"); mediaType.Encoding = System.Text.Encoding.UTF8; httpResponse.ContentType = mediaType.ToString(); //设置导出文件名 httpResponse.Headers.Add("content-disposition", $"attachment;filename={excelName}.xls"); MemoryStream ms = new MemoryStream(); //这句代码非常重要，如果不加，会报：打开的EXCEL格式与扩展名指定的格式不一致 ms.Seek(0, SeekOrigin.Begin); workbook.Write(ms); byte[] myByteArray = ms.GetBuffer(); httpResponse.Headers.Add("Content-Length", myByteArray.Length.ToString()); await httpResponse.Body.WriteAsync(myByteArray, 0, myByteArray.Length); } /// <summary> /// 根据属性名顺序获取对应的属性对象 /// </summary> /// <param name="fieldNameList"></param> /// <returns></returns> private Dictionary<int, PropertyInfo> GetIndexPropertyDic(List<string> fieldNameList) { Dictionary<int, PropertyInfo> indexPropertyDic = new Dictionary<int, PropertyInfo>(fieldNameList.Count); List<PropertyInfo> tPropertyInfoList = typeof(T).GetProperties().ToList(); PropertyInfo propertyInfo = null; for (int i = 0; i < fieldNameList.Count; i++) { propertyInfo = tPropertyInfoList.Find(m => m.Name.Equals(fieldNameList[i], StringComparison.OrdinalIgnoreCase)); indexPropertyDic.Add(i, propertyInfo); } return indexPropertyDic; } }