C#-微信公众平台接口-上传临时素材

转：http://blog.niunan.net/blog/show/1212

最烦做微信公众平台的东西。。文档说得不清不楚，又没示例代码，只能自己 慢慢搜索，弄了一晚上，基本弄出来了，把本地的图片上传到微信的临时素材那里，返回媒体ID，用于其他操作，代码如下 ：（自己导入相应的类System.Net.Http，JSON解析用的LitJson）

       /// <summary>
        /// 上传临时素材
        /// 返回media_id
        /// </summary>
        /// <param name="userid"></param>
        /// <returns></returns>
        public string UploadLinShiSuCai(int userid) {
            string imgpath = HttpContext.Current.Server.MapPath($"/upload/erweima/{userid}_2.png");
            string appid = WxPayConfig.APPID;
            string secret = WxPayConfig.APPSECRET;

            //1. 获取AccessToken（有效期7200秒，开发者必须在自己的服务全局缓存access_token）
            string url1 = $"https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid={appid}&secret={secret}";
            string result = HttpService.Get(url1);
            JsonData jd = JsonMapper.ToObject(result);
            string access_token = (string)jd["access_token"];

            string url2 = $"https://api.weixin.qq.com/cgi-bin/media/upload?access_token={access_token}&type=image";

            //图片转为流
            Image img = new Bitmap(imgpath);
            MemoryStream stream = new MemoryStream();
            img.Save(stream, ImageFormat.Png);
            BinaryReader br = new BinaryReader(stream);
            byte[] data = stream.ToArray();
            stream.Close();



            var boundary = "fbce142e-4e8e-4bf3-826d-cc3cf506cccc";
            var client = new HttpClient();
            client.DefaultRequestHeaders.Add("User-Agent", "KnowledgeCenter");
            client.DefaultRequestHeaders.Remove("Expect");
            client.DefaultRequestHeaders.Remove("Connection");
            client.DefaultRequestHeaders.ExpectContinue = false;
            client.DefaultRequestHeaders.ConnectionClose = true;
            var content = new MultipartFormDataContent(boundary);
            content.Headers.Remove("Content-Type");
            content.Headers.TryAddWithoutValidation("Content-Type", "multipart/form-data; boundary=" + boundary);
            var contentByte = new ByteArrayContent(data);
            content.Add(contentByte);
            contentByte.Headers.Remove("Content-Disposition");
            contentByte.Headers.TryAddWithoutValidation("Content-Disposition", $"form-data; name="media";filename="{userid}_2.png"" + "");
            contentByte.Headers.Remove("Content-Type");
            contentByte.Headers.TryAddWithoutValidation("Content-Type", "image/png");
            try
            {
                var result2 = client.PostAsync(url2, content);
                if (result2.Result.StatusCode != HttpStatusCode.OK)
                    throw new Exception(result2.Result.Content.ReadAsStringAsync().Result);
                string jsonstr = result2.Result.Content.ReadAsStringAsync().Result;
                JsonData jd2 = JsonMapper.ToObject(jsonstr);
                result = (string)jd2["media_id"];
                return result;
            }
            catch (Exception ex)
            {
                throw new Exception(ex.Message + ex.InnerException.Message);
            } 

        }
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