涉及access_token的獲取請參考《C#微信公眾平臺開發之access_token的獲取存儲與更新》
一、為了實現高級群發功能，需要解決的問題
1、通過微信接口上傳圖文消息素材時，Json中的圖片不是url而是media_id，如何通過微信接口上傳圖片并獲取圖片的media_id？
2、圖片存儲在什么地方，如何獲?。?/p>
二、實現步驟，以根據OpenID列表群發圖文消息為例
1、準備數據
我把數據存儲在數據庫中，ImgUrl字段是圖片在服務器上的相對路徑(這里的服務器是自己的服務器，不是微信的哦)。
從數據庫中獲取數據放到DataTable中：
DataTable dt = ImgItemDal.GetImgItemTable(loginUser.OrgID, data);
2、通過微信接口上傳圖片，返回圖片的media_id
取ImgUrl字段數據，通過MapPath方法獲取圖片在服務器上的物理地址，用FileStream類讀取圖片，并上傳給微信
HTTP上傳文件代碼(HttpRequestUtil類)：
/// <summary>/// Http上傳文件/// </summary>public static string HttpUploadFile(string url, string path){ // 設置參數 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"); // 隨機分隔線 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("http://"); string fileName = path.Substring(pos + 1); //請求頭部信息 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(); //發送請求并獲取相應回應數據 HttpWebResponse response = request.GetResponse() as HttpWebResponse; //直到request.GetResponse()程序才開始向目標網頁發送Post請求 Stream instream = response.GetResponseStream(); StreamReader sr = new StreamReader(instream, Encoding.UTF8); //返回結果網頁（html）代碼 string content = sr.ReadToEnd(); return content;}請求微信接口，上傳圖片，返回media_id(WXApi類)：
/// <summary>/// 上傳媒體返回媒體ID/// </summary>public static string UploadMedia(string access_token, string type, string path){ // 設置參數 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); // 上圖片返回媒體IDstring media_id = Tools.GetJsonValue(msg, "media_id");
傳入的path(aspx.cs文件中的代碼)：
string path = MapPath(data);
一個圖文消息由若干條圖文組成，每條圖文有標題、內容、鏈接、圖片等
遍歷每條圖文數據，分別請求微信接口，上傳圖片，獲取media_id
3、上傳圖文消息素材
拼接圖文消息素材Json字符串(ImgItemDal類(操作圖文消息表的類))：
/// <summary>/// 拼接圖文消息素材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/":/"要發送的圖片不存在/"}"; } string msg = WXApi.UploadMedia(access_token, "image", path); // 上圖片返回媒體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();}上傳圖文消息素材，獲取圖文消息的media_id：
/// <summary>/// 請求Url，發送數據/// </summary>public static string PostUrl(string url, string postData){ byte[] data = Encoding.UTF8.GetBytes(postData); // 設置參數 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 = request.GetRequestStream(); outstream.Write(data, 0, data.Length); outstream.Close(); //發送請求并獲取相應回應數據 HttpWebResponse response = request.GetResponse() as HttpWebResponse; //直到request.GetResponse()程序才開始向目標網頁發送Post請求 Stream instream = response.GetResponseStream(); StreamReader sr = new StreamReader(instream, Encoding.UTF8); //返回結果網頁（html）代碼 string content = sr.ReadToEnd(); return content;}/// <summary>/// 上傳圖文消息素材返回media_id/// </summary>public static string UploadNews(string access_token, string postData){ return HttpRequestUtil.PostUrl(string.Format("https://api.weixin.qq.com/cgi-bin/media/uploadnews?access_token={0}", access_token), postData);}string articlesJson = ImgItemDal.GetArticlesJsonStr(this, access_token, dt);string newsMsg = WXApi.UploadNews(access_token, articlesJson);string newsid = Tools.GetJsonValue(newsMsg, "media_id");
4、群發圖文消息
獲取全部關注者OpenID集合(WXApi類)：
/// <summary>/// 獲取關注者OpenID集合/// </summary>public static List<string> GetOpenIDs(string access_token){ List<string> result = new List<string>(); List<string> openidList = GetOpenIDs(access_token, null); result.AddRange(openidList); while (openidList.Count > 0) { openidList = GetOpenIDs(access_token, openidList[openidList.Count - 1]); result.AddRange(openidList); } return result;}/// <summary>/// 獲取關注者OpenID集合/// </summary>public static List<string> GetOpenIDs(string access_token, string next_openid){ // 設置參數 string url = string.Format("https://api.weixin.qq.com/cgi-bin/user/get?access_token={0}&next_openid={1}", access_token, string.IsNullOrWhiteSpace(next_openid) ? "" : next_openid); string returnStr = HttpRequestUtil.RequestUrl(url); int count = int.Parse(Tools.GetJsonValue(returnStr, "count")); if (count > 0) { string startFlg = "/"openid/":["; int start = returnStr.IndexOf(startFlg) + startFlg.Length; int end = returnStr.IndexOf("]", start); string openids = returnStr.Substring(start, end - start).Replace("/"", ""); return openids.Split(',').ToList<string>(); } else { return new List<string>(); }}List<string> openidList = WXApi.GetOpenIDs(access_token); //獲取關注者OpenID列表
拼接圖文消息Json(WXMsgUtil類)：
/// <summary>/// 圖文消息json/// </summary>public static string CreateNewsJson(string media_id, List<string> openidList){ StringBuilder sb = new StringBuilder(); sb.Append("{/"touser/":["); sb.Append(string.Join(",", openidList.ConvertAll<string>(a => "/"" + a + "/"").ToArray())); sb.Append("],"); sb.Append("/"msgtype/":/"mpnews/","); sb.Append("/"mpnews/":{/"media_id/":/"" + media_id + "/"}"); sb.Append("}"); return sb.ToString();}群發代碼：
resultMsg = WXApi.Send(access_token, WXMsgUtil.CreateNewsJson(newsid, openidList));/// <summary>/// 根據OpenID列表群發/// </summary>public static string Send(string access_token, string postData){ return HttpRequestUtil.PostUrl(string.Format("https://api.weixin.qq.com/cgi-bin/message/mass/send?access_token={0}", access_token), postData);}供群發按鈕調用的方法(data是傳到頁面的id，根據它從數據庫中取數據)：
/// <summary>/// 群發/// </summary>public string Send(){ string type = Request["type"]; string data = Request["data"]; string access_token = AdminUtil.GetAccessToken(this); //獲取access_token List<string> openidList = WXApi.GetOpenIDs(access_token); //獲取關注者OpenID列表 UserInfo loginUser = AdminUtil.GetLoginUser(this); //當前登錄用戶 string resultMsg = null; //發送文本 if (type == "1") { resultMsg = WXApi.Send(access_token, WXMsgUtil.CreateTextJson(data, openidList)); } //發送圖片 if (type == "2") { string path = MapPath(data); if (!File.Exists(path)) { return "{/"code/":0,/"msg/":/"要發送的圖片不存在/"}"; } string msg = WXApi.UploadMedia(access_token, "image", path); string media_id = Tools.GetJsonValue(msg, "media_id"); resultMsg = WXApi.Send(access_token, WXMsgUtil.CreateImageJson(media_id, openidList)); } //發送圖文消息 if (type == "3") { DataTable dt = ImgItemDal.GetImgItemTable(loginUser.OrgID, data); string articlesJson = ImgItemDal.GetArticlesJsonStr(this, access_token, dt); string newsMsg = WXApi.UploadNews(access_token, articlesJson); string newsid = Tools.GetJsonValue(newsMsg, "media_id"); resultMsg = WXApi.Send(access_token, WXMsgUtil.CreateNewsJson(newsid, openidList)); } //結果處理 if (!string.IsNullOrWhiteSpace(resultMsg)) { string errcode = Tools.GetJsonValue(resultMsg, "errcode"); string errmsg = Tools.GetJsonValue(resultMsg, "errmsg"); if (errcode == "0") { return "{/"code/":1,/"msg/":/"/"}"; } else { return "{/"code/":0,/"msg/":/"errcode:" + errcode + ", errmsg:" + errmsg + "/"}"; } } else { return "{/"code/":0,/"msg/":/"type參數錯誤/"}"; }}精彩專題分享：ASP.NET微信開發教程匯總，歡迎大家學習。
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