npm install xlsx --save

import * as XLSX from 'xlsx';

import * as XLSX from 'xlsx';

excelData = [];

importExcel(evt: any) {
  /* wire up file reader */
  const target: DataTransfer = <DataTransfer>(evt.target);
  if (target.files.length !== 1) throw new Error('Cannot use multiple files');
  const reader: FileReader = new FileReader();
  reader.onload = (e: any) => {
   /* read workbook */
   const bstr: string = e.target.result;
   const wb: XLSX.WorkBook = XLSX.read(bstr, { type: 'binary' });

   /* grab first sheet */
   const wsname: string = wb.SheetNames[0];
   const ws: XLSX.WorkSheet = wb.Sheets[wsname];

   /* save data */
   this.excelData = (XLSX.utils.sheet_to_json(ws, { header: 1 }));

   evt.target.value = "" // 清空
  };
  reader.readAsBinaryString(target.files[0]);

 }

exportExcel(codeList: string[]) {
  return this.http.post(this.ExportExcelByCodesUrl, codeList, {
   responseType: 'arraybuffer',//设置响应类型
   observe:"response",//返回response header
   headers: { 'Content-Type': 'application/json' }
  })
   .subscribe((response:any)=>{
    this.downLoadFile(response, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet;charset=utf-8")
   })

 }

 /**
  * Method is use to download file.
  * @param data - Array Buffer data
  * @param type - type of the document.
 */
downLoadFile(data: any, type: string) {
   var blob = new Blob([data.body], { type: type});
   let downloadElement = document.createElement('a');
   let href = window.URL.createObjectURL(blob); //创建下载的链接
   downloadElement.href = href;
   let filename = data.headers.get("Download-FileName");//后端返回的自定义header
   downloadElement.download = decodeURI(filename); 

   document.body.appendChild(downloadElement);
   downloadElement.click(); //点击下载
   document.body.removeChild(downloadElement); //下载完成移除元素
   window.URL.revokeObjectURL(href); //释放掉blob对象
 }

public IActionResult CreateExcel(string fileName,List<ExportProductModel> list)
 {
  string[] propertyNames = {""};//业务代码
  string[] propertyNameCn = {""};//业务代码
  MemoryStream ms = ExcelsHelper<ExportProductModel>.ListToExcel(fileName, list, propertyNames, propertyNameCn);
  HttpContext.Response.Headers.Add("Download-FileName",WebUtility.UrlEncode(fileName));
  return File(ms, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet;", WebUtility.UrlEncode(fileName));
 }

services.AddCors(options =>
         {
          options.AddPolicy("AllowAllOrigin", builder =>
                   {
                    builder.AllowAnyHeader()
                     .AllowAnyMethod()
                     .AllowAnyOrigin()
                     .AllowCredentials()
                     .WithExposedHeaders("Download-FileName"); 

                   });
         });