.NET实现微信公共平台上传下载多媒体文件

/// <SUMMARY> 
  /// 下载保存多媒体文件,返回多媒体保存路径 
  /// </SUMMARY> 
  /// <PARAM name="ACCESS_TOKEN"></PARAM> 
  /// <PARAM name="MEDIA_ID"></PARAM> 
  /// <RETURNS></RETURNS> 
  public string GetMultimedia(string ACCESS_TOKEN, string MEDIA_ID) 
  { 
    string file = string.Empty; 
    string content = string.Empty; 
    string strpath = string.Empty; 
    string savepath = string.Empty; 
    string stUrl = "http://file.api.weixin.qq.com/cgi-bin/media/get?access_token=" + ACCESS_TOKEN + "&media_id=" + MEDIA_ID; 
 
    HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(stUrl); 
 
    req.Method = "GET"; 
    using (WebResponse wr = req.GetResponse()) 
    { 
      HttpWebResponse myResponse = (HttpWebResponse)req.GetResponse(); 
 
      strpath = myResponse.ResponseUri.ToString(); 
      WriteLog("接收类别://" + myResponse.ContentType); 
      WebClient mywebclient = new WebClient(); 
      savepath = Server.MapPath("image") + "\\" + DateTime.Now.ToString("yyyyMMddHHmmssfff") + (new Random()).Next().ToString().Substring(0, 4) + ".jpg"; 
      WriteLog("路径://" + savepath); 
      try
      { 
        mywebclient.DownloadFile(strpath, savepath); 
        file = savepath; 
      } 
      catch (Exception ex) 
      { 
        savepath = ex.ToString(); 
      } 
 
    } 
    return file; 
  } 

class wxmessage  
 {  
   public string FromUserName { get; set; }  
   public string ToUserName { get; set; }  
    public string MsgType { get; set; }  
    public string EventName { get; set; }  
    public string Content { get; set; } 
    public string Recognition { get; set; } 
    public string MediaId { get; set; } 
    public string EventKey { get; set; } 
  } 

private wxmessage GetWxMessage() 
   { 
     wxmessage wx = new wxmessage(); 
     StreamReader str = new StreamReader(Request.InputStream, System.Text.Encoding.UTF8); 
     XmlDocument xml = new XmlDocument(); 
     xml.Load(str); 
     wx.ToUserName = xml.SelectSingleNode("xml").SelectSingleNode("ToUserName").InnerText; 
     wx.FromUserName = xml.SelectSingleNode("xml").SelectSingleNode("FromUserName").InnerText; 
     wx.MsgType = xml.SelectSingleNode("xml").SelectSingleNode("MsgType").InnerText; 
     if (wx.MsgType.Trim() == "text") 
     { 
       wx.Content = xml.SelectSingleNode("xml").SelectSingleNode("Content").InnerText; 
     } 
     if (wx.MsgType.Trim() == "event") 
     { 
       wx.EventName = xml.SelectSingleNode("xml").SelectSingleNode("Event").InnerText; 
       wx.EventKey = xml.SelectSingleNode("xml").SelectSingleNode("EventKey").InnerText; 
     } 
     if (wx.MsgType.Trim() == "voice") 
     { 
       wx.Recognition = xml.SelectSingleNode("xml").SelectSingleNode("Recognition").InnerText; 
     } 
    if (wx.MsgType.Trim() == "image") 
    { 
      wx.MediaId = xml.SelectSingleNode("xml").SelectSingleNode("MediaId").InnerText; 
    } 
      
     return wx; 
   } 

/// <SUMMARY> 
  /// 上传多媒体文件,返回 MediaId 
  /// </SUMMARY> 
  /// <PARAM name="ACCESS_TOKEN"></PARAM> 
  /// <PARAM name="Type"></PARAM> 
  /// <RETURNS></RETURNS> 
  public string UploadMultimedia(string ACCESS_TOKEN, string Type) 
  { 
    string result = ""; 
    string wxurl = "http://file.api.weixin.qq.com/cgi-bin/media/upload?access_token=" + ACCESS_TOKEN + "&type=" + Type; 
    string filepath = Server.MapPath("image") + "\\hemeng80.jpg";(本地服务器的地址) 
    WriteLog("上传路径:" + filepath); 
    WebClient myWebClient = new WebClient(); 
    myWebClient.Credentials = CredentialCache.DefaultCredentials; 
    try
    { 
      byte[] responseArray = myWebClient.UploadFile(wxurl, "POST", filepath); 
      result = System.Text.Encoding.Default.GetString(responseArray, 0, responseArray.Length); 
      WriteLog("上传result:" + result); 
      UploadMM _mode = JsonHelper.ParseFromJson<UPLOADMM>(result); 
      result = _mode.media_id; 
    } 
    catch (Exception ex) 
    { 
      result = "Error:" + ex.Message; 
    } 
    WriteLog("上传MediaId:" + result); 
    return result; 
  } 

protected string sendPicTextMessage(Msg _mode, string MediaId) 
  { 
    string res = string.Format(@"<xml>
                      <ToUserName><![CDATA[{0}]]></ToUserName>
                      <FromUserName><![CDATA[{1}]]></FromUserName>
                      <CreateTime>{2}</CreateTime>
                      <MsgType><![CDATA[image]]></MsgType>
                      <Image>
                      <MediaId><![CDATA[{3}]]></MediaId>
                      </Image>
                  </xml> ", 
      _mode.FromUserName, _mode.ToUserName, DateTime.Now, MediaId); 
 
    return res; 
  }