public async Task<IActionResult> FileSave()
        {
            var files = Request.Form.Files;
            long size = files.Sum(f => f.Length);
            string webRootPath = _hostingEnvironment.WebRootPath;
            string contentRootPath = _hostingEnvironment.ContentRootPath;

            List<Tuple<string, string, string>> result = new List<Tuple<string, string, string>>();

            foreach (var formFile in files)
            {
                if (formFile.Length > 0)
                {
                    string fileExt = Path.GetExtension(formFile.FileName);

                    long fileSize = formFile.Length; //获得文件大小，以字节为单位
                    string newFileName = formFile.FileName.Replace(fileExt, "") + '_' + System.Guid.NewGuid().ToString() + fileExt;//随机生成新的文件名

                    //物理路径
                    var phyfilePath = $"{webRootPath}\\upload\\";

                    if (System.IO.Directory.Exists(phyfilePath) == false)//如果不存在就创建file文件夹
                    {
                        System.IO.Directory.CreateDirectory(phyfilePath);
                    }
                    using (var stream = new FileStream(phyfilePath + newFileName, FileMode.Create))
                    {
                        await formFile.CopyToAsync(stream);
                    }
                    //前台访问路径
                    var filePath = $"{Request.Host}/upload/{newFileName}";
                    result.Add(Tuple.Create(formFile.FileName, fileExt, filePath));
                }
            }
            return Ok(new { files.Count, result });
        }