C#微信公众平台开发—高级群发接口

涉及access_token的获取请参考《C#微信公众平台开发—access_token的获取存储与更新》

一、为了实现高级群发功能，需要解决的问题

1、通过微信接口上传图文消息素材时，Json中的图片不是url而是media_id，如何通过微信接口上传图片并获取图片的media_id？

2、图片存储在什么地方，如何获取？

二、实现步骤，以根据OpenID列表群发图文消息为例

1、准备数据

我把数据存储在数据库中，ImgUrl字段是图片在服务器上的相对路径(这里的服务器是自己的服务器，不是微信的哦)。

从数据库中获取数据放到DataTable中：

DataTable dt = ImgItemDal.GetImgItemTable(loginUser.OrgID, data);

2、通过微信接口上传图片，返回图片的media_id

取ImgUrl字段数据，通过MapPath方法获取图片在服务器上的物理地址，用FileStream类读取图片，并上传给微信

HTTP上传文件代码(HttPRequestUtil类)：

/// <summary>/// Http上传文件/// </summary>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("/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);    //返回结果网页（html）代码    string content = sr.ReadToEnd();    return content;}

请求微信接口，上传图片，返回media_id(WXApi类)：

/// <summary>/// 上传媒体返回媒体ID/// </summary>public static string UploadMedia(string access_token, string type, string path){    // 设置参数    string url = string.Format("http://file.api.weixin.QQ.com/cgi-bin/media/upload?access_token={0}&type={1}", access_token, type);    return HttpRequestUtil.HttpUploadFile(url, path);}

string msg = WXApi.UploadMedia(access_token, "image", path); // 上图片返回媒体IDstring media_id = Tools.GetJsonValue(msg, "media_id");

传入的path(aspx.cs文件中的代码)：

string path = MapPath(data);

一个图文消息由若干条图文组成，每条图文有标题、内容、链接、图片等

遍历每条图文数据，分别请求微信接口，上传图片，获取media_id

3、上传图文消息素材

拼接图文消息素材Json字符串(ImgItemDal类(操作图文消息表的类))：

/// <summary>/// 拼接图文消息素材Json字符串/// </summary>public static string GetArticlesJsonStr(PageBase page, string access_token, DataTable dt){    StringBuilder sbArticlesJson = new StringBuilder();    sbArticlesJson.Append("{/"articles/":[");    int i = 0;    foreach (DataRow dr in dt.Rows)    {        string path = page.MapPath(dr["ImgUrl"].ToString());        if (!File.Exists(path))        {            return "{/"code/":0,/"msg/":/"要发送的图片不存在/"}";        }        string msg = WXApi.UploadMedia(access_token, "image", path); // 上图片返回媒体ID        string media_id = Tools.GetJsonValue(msg, "media_id");        sbArticlesJson.Append("{");        sbArticlesJson.Append("/"thumb_media_id/":/"" + media_id + "/",");        sbArticlesJson.Append("/"author/":/"" + dr["Author"].ToString() + "/",");        sbArticlesJson.Append("/"title/":/"" + dr["Title"].ToString() + "/",");        sbArticlesJson.Append("/"content_source_url/":/"" + dr["TextUrl"].ToString() + "/",");        sbArticlesJson.Append("/"content/":/"" + dr["Content"].ToString() + "/",");        sbArticlesJson.Append("/"digest/":/"" + dr["Content"].ToString() + "/",");        if (i == dt.Rows.Count - 1)        {            sbArticlesJson.Append("/"show_cover_pic/":/"1/"}");        }        else        {            sbArticlesJson.Append("/"show_cover_pic/":/"1/"},");        }        i++;    }    sbArticlesJson.Append("]}");    return sbArticlesJson.ToString();}

上传图文消息素材，获取图文消息的media_id：

/// <summary>/// 请求Url，发送数据/// </summary>public static string PostUrl(string url, string postData){    byte[] data = Encoding.UTF8.GetBytes(postData);    // 设置参数    HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;    CookieContainer cookieContainer = new CookieContainer();    request.CookieContainer = cookieContainer;    request.AllowAutoRedirect = true;    request.Method = "POST";    request.ContentType = "application/x-www-form-urlencoded";    request.ContentLength = data.Length;    Stream outstream = re