public string PostFile([FromForm] IFormCollection formCollection)
        {
            var files = formCollection.Files;

            String RandFileName = "";

            if (files.Count == 0)
            {
                RandFileName = "找不到上传的文件";
            }
            foreach (var formFile in files)
            {
                RandFileName = _FileUploadService.PostFile(formFile);
            }

            return(RandFileName);
        }