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;
 }