微信发送永久图片素材接口----详解

本文采用倒叙模式.

我写这个主要是因为微信开发文档的说明实在太坑了，为了更多.NET 开发人员能顺利上传微信图片素材，分享一下：

先看看最后的调用成功的方法： 

/// <summary>

        /// 发送永久图片素材

        /// </summary>

        /// <param name="filename">文件绝对路径</param>

        public static void PushtPicture(string filename)

        {

            var accessToken = new WxHelper().totalAccessToken;

            var postUrl = string.Format("https://api.weixin.qq.com/cgi-bin/material/add_material?access_token={0}", accessToken);

           NameValueCollection myCol =new NameValueCollection();

            //MD，第三个参数必须是media,,否则上传失败,真操蛋

           var response = JsonConvert.DeserializeObject<WxPictureResp>(HttpProcess.HttpUploadFile(postUrl, filename, "media", "image/jpeg", myCol));

        }

ok,再上微信版模拟http发送文件:

 /// <summary>

        /// 模拟http发送文件，这里只发送图片

        /// </summary>

        /// <param name="url">发送的url地址</param>

        /// <param name="">文件绝对路径</param>

        /// <param name="paramName">这里必须是media</param>

        /// <param name="contentType">是图片，视频还是啥，自己去看http传文件格式</param>

        /// <param name="nvc">可不填</param>

        /// <returns></returns>

 public static string HttpUploadFile(string url, string , string paramName, string contentType, NameValueCollection nvc)

        {

            string result = string.Empty;

            string boundary = "---------------------------" DateTime.Now.Ticks.ToString("x");

            byte[] boundarybytes = System.Text.Encoding.ASCII.GetBytes("\r\n--" boundary "\r\n");

            HttpWebRequest wr = (HttpWebRequest)WebRequest.Create(url);

            wr.ContentType = "multipart/form-data; boundary=" boundary;

            wr.Method = "POST";

            wr.KeepAlive = true;

            wr.Credentials = System.Net.CredentialCache.DefaultCredentials;

            Stream rs = wr.GetRequestStream();

            string formdataTemplate = "Content-Disposition: form-data; name=\"{0}\"\r\n\r\n{1}";

            foreach (string key in nvc.Keys)

            {

                rs.Write(boundarybytes, 0, boundarybytes.Length);

                string formitem = string.Format(formdataTemplate, key, nvc[key]);

                byte[] formitembytes = System.Text.Encoding.UTF8.GetBytes(formitem);

                rs.Write(formitembytes, 0, formitembytes.Length);

            }

            rs.Write(boundarybytes, 0, boundarybytes.Length);

            string headerTemplate = "Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"\r\nContent-Type: {2}\r\n\r\n";

            var pos = .LastIndexOf('/');

            var filename = .Substring(pos 1);

            string header = string.Format(headerTemplate, paramName, filename, contentType);

            byte[] headerbytes = System.Text.Encoding.UTF8.GetBytes(header);

            rs.Write(headerbytes, 0, headerbytes.Length);

            FileStream fileStream = new FileStream(, FileMode., FileAccess.Read);

            byte[] buffer = new byte[4096];

            int bytesRead = 0;

            while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)

            {

                rs.Write(buffer, 0, bytesRead);

            }

            fileStream.();

            byte[] trailer = System.Text.Encoding.ASCII.GetBytes("\r\n--" boundary "--\r\n");

            rs.Write(trailer, 0, trailer.Length);

            rs.Flush();

            rs.();

            WebResponse wresp = null;

            try

            {

                wresp = wr.GetResponse();

                Stream stream2 = wresp.GetResponseStream();

                StreamReader reader2 = new StreamReader(stream2);

                result = reader2.ReadToEnd();

            }

            catch (Exception ex)

            {

                if (wresp != null)

                {

                    wresp.();

                    wresp = null;

                }

            }

            finally

            {

                wr = null;

            }

            result;

        }

最后上工具类：

/// <summary>

    /// 微信服务器返回的图片类，只记录成功，失败为null

    /// </summary>

    public class WxPictureResp

    {

        /// <summary>

        /// 这个就是能用来构造图文消息的 thumb_media_id

        /// </summary>

        public string media_id { get; ; }

        /// <summary>

        /// 图片路径,只能在TX系的域名中使用

        /// </summary>

        public string url { get; ; }

    }

可能模拟http发送文件的类有点low，至少应该用StringBuilder的,懒得改了，不差这点性能。

最后

var accessToken = new WxHelper().totalAccessToken;

这个应该不用说,这里采用了Redis缓存，没法用静态构造,只好new啦.