关于微信公众号上传永久素材接口的问题

　　最近在做关于微信公众号接口的问题，发现上传永久素材的地方有些小问题。

1.临时素材和永久素材没有关系，在微信服务器可以保存三天。新增的临时素材只能通过media_id（临时素材）获取。

2.新增图文素材以外的素材，需要使用‘新增其他类型永久素材’接口，其中文档写的地址为

　　http请求方式: POST，需使用https https://api.weixin.qq.com/cgi-bin/material/add_material?access_token=ACCESS_TOKEN

　　在测试的过程中发现，少了type属性。我之前一直用json对象传值进去，所以总是出现各种错误。

　　通过这个接口就可以获得到media_id（永久素材）。

3.上传需要使用multipart/form-data方式。

下面是代码，在网上搜了一些高手的方法，稍微进行了一下组合，亲测可用

        /// <summary>
        /// 新增永久素材
        /// </summary>
        /// <param name="form"></param>
        /// <returns></returns>
        [HttpPost]
        public string UploadLong(FormCollection form)
        {

            if (Request.Files.Count == 0)
            {
                //Request.Files.Count 文件数为0上传不成功
                return "文件数为0上传不成功";
            }
            var file = Request.Files[0];
            if (file.ContentLength == 0)
            {
                //文件大小（以字节为单位）为0时，做一些操作
                return "文件大小（以字节为单位）为0";
            }
            else
            {
                //文件大小不为0
                HttpPostedFileBase files = Request.Files[0];
                string type = "image";
                string url = string.Format("http://api.weixin.qq.com/cgi-bin/material/add_material?access_token={0}&type={1}", token, type.ToString());
                string path = "C://Users//xjh//Desktop//img//" + files.FileName;
                //服务器上的UpLoadFile文件夹必须有读写权限　　　　　　
                files.SaveAs(path);
                string filename = System.Web.HttpContext.Current.Server.MapPath("/image/" + files.FileName);
                //返回url
                //var geturl = HttpUploadFile(string.Format("https://api.weixin.qq.com/cgi-bin/media/uploadimg?access_token={0}", token), file.FileName);
                string json = HttpUploadFile(url, filename);
                JObject jb = (JObject)JsonConvert.DeserializeObject(json);
                //todo
                return json;
            }
        }

以下为post方法

        public static string HttpUploadFile(string url, string path) 
        {
            // 设置参数
            HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
            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("
--" + boundary + "
");
            byte[] endBoundaryBytes = Encoding.UTF8.GetBytes("
--" + boundary + "--
");

            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="media";filename="{0}"
Content-Type:application/octet-stream

",
                        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);
            //返回结果网页（html）代码
            string content = sr.ReadToEnd();
            return content;
        }