语音识别这个功能属于高级功能，必须微信实名认证后才能实现，认证费用300元/年，如果你作为开发者可以申请测试帐号，也是可以的。首先建立一个微信消息类，这个类比之前多了一个属性。

 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 EventKey { get; set; } 
    }

语音识别是微信自带的功能，非常强大无需我们做过多的操作：

protected void Page_Load(object sender, EventArgs e)
     {
         wxmessage wx = GetWxMessage();
         string res = "";

         if (!string.IsNullOrEmpty(wx.EventName) && wx.EventName.Trim() == "subscribe")
         {//刚关注时的时间，用于欢迎词
             string content = "";
             content = "/:rose欢迎北京永杰友信科技有限公司/:rose\n直接回复“你好”";
             res = sendTextMessage(wx, content);
         }
         else
         {
             if (wx.MsgType == "text" && wx.Content == "你好")
             {
                 res = sendTextMessage(wx, "你好,欢迎使用北京永杰友信科技有限公司公共微信平台!");
             }
             else if (wx.MsgType == "voice")//识别消息类型为语音
             {
                 res = sendTextMessage(wx, wx.Recognition);//wx.Recognition就是语音识别的结果了，我们直接引用，以文本形式反馈就OK了

             }
             else
             {
                 res = sendTextMessage(wx, "你好,未能识别消息!");
             }
         }

         Response.Write(res);
     }

 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;
         }
         if (wx.MsgType.Trim() == "voice")//如果是语音消息的话就把识别结果赋值给实体类的相应属性Recognition 
         {
             wx.Recognition = xml.SelectSingleNode("xml").SelectSingleNode("Recognition").InnerText;
         }
         
         return wx;
     }


     /// 
  
     /// 发送文字消息  
     /// 
  
     /// 获取的收发者信息  
     /// 内容  
     /// 
  
    
     private string sendTextMessage(wxmessage wx, string content)
     {
         string res = string.Format(@" ",
             wx.FromUserName, wx.ToUserName, DateTime.Now, content);
         return res;
     }