.net core3.1 WebAPI使用HttpClient为企业微信上传临时素材

   /// <summary>
        /// 上传临时素材
        /// </summary>
        /// <param name="file">文件(文件名中文有乱码问题）</param>
        /// <returns></returns>
        [HttpPost]
        public async Task<IActionResult> UploadMedia(IFormFile file)
        {
            var tokenResult = GetQYAccessToken().Result;
            dynamic resultObj = JsonConvert.DeserializeObject(tokenResult);
            var url = string.Format("https://qyapi.weixin.qq.com/cgi-bin/media/upload?access_token={0}&type={1}", resultObj.access_token, file.Name);
            //读取上载文件流
            var stream = file.OpenReadStream();
            byte[] data = new byte[stream.Length];
            stream.Read(data, 0, data.Length);
            stream.Close();

            var boundary = DateTime.Now.Ticks.ToString("X");// 随机分隔线
            var content = new MultipartFormDataContent(boundary);
            content.Headers.Remove("Content-Type");
            content.Headers.TryAddWithoutValidation("Content-Type", "multipart/form-data; boundary=" + boundary);

            HttpContent byteContent = new ByteArrayContent(data);
            content.Add(byteContent);
            byteContent.Headers.Remove("Content-Disposition");
            byteContent.Headers.TryAddWithoutValidation("Content-Disposition", $"form-data; name=\"media\";filename=\"{file.FileName}\"" + "");
            byteContent.Headers.Remove("Content-Type");
            byteContent.Headers.TryAddWithoutValidation("Content-Type", "application/octet-stream");

            var client = _httpClientFactory.CreateClient();