企业微信上传临时素材

public static QiyeMaterialMsg UploadQyImg(string path)
        {
            try
            {
                HttpWebRequest request = WebRequest.Create($"https://qyapi.weixin.qq.com/cgi-bin/media/upload?access_token={Config.access_token}&type=image") as HttpWebRequest;

                if (request != null)
                {
                    CookieContainer cookieContainer = new CookieContainer();
                    request.CookieContainer = cookieContainer;
                    request.AllowAutoRedirect = true;
                    request.Method = "POST";
                    string boundary = DateTime.Now.Ticks.ToString("X"); // 随机分隔线
                    request.ContentType = "multipart/form-data;charset=utf-8;boundary=" + boundary;
                    byte[] itemBoundaryBytes = Encoding.UTF8.GetBytes("\r\n--" + boundary + "\r\n");
                    byte[] endBoundaryBytes = Encoding.UTF8.GetBytes("\r\n--" + boundary + "--\r\n");

                    int pos = path.LastIndexOf("\\");
                    string fileName = path.Substring(pos + 1);

                    //请求头部信息
                    StringBuilder sbHeader = new StringBuilder(string.Format("Content-Disposition:form-data;name=\"file\";filename=\"{0}\"\r\nContent-Type:application/octet-stream\r\n\r\n", fileName));
                    byte[] postHeaderBytes = Encoding.UTF8.GetBytes(sbHeader.ToString());

                    FileStream fs = new FileStream(path, FileMode.Open, FileAccess.Read);
                    byte[] bArr = new byte[fs.Length];
                    fs.Read(bArr, 0, bArr.Length);
                    fs.Close();

                    Stream postStream = request.GetRequestStream();
                    postStream.Write(itemBoundaryBytes, 0, itemBoundaryBytes.Length);
                    postStream.Write(postHeaderBytes, 0, postHeaderBytes.Length);
                    postStream.Write(bArr, 0, bArr.Length);
                    postStream.Write(endBoundaryBytes, 0, endBoundaryBytes.Length);
                    postStream.Close();

                    //发送请求并获取相应回应数据
                    HttpWebResponse response = request.GetResponse() as HttpWebResponse;
                    //直到request.GetResponse()程序才开始向目标网页发送Post请求
                    Stream instream = response.GetResponseStream();
                    StreamReader sr = new StreamReader(instream, Encoding.UTF8);
                    string content = sr.ReadToEnd();
                    return JsonHelper.JsonDeserialize<QiyeMaterialMsg>(content);
                }

                return new QiyeMaterialMsg();
            }
            catch (Exception e)
            {
                LogHelper.ErrorLog(e.Message);
                return new QiyeMaterialMsg { errmsg = e.Message };
            }
        }