C# WeChat public account development--WeChat event interaction

[HttpGet][ActionName("Index")]
public ActionResult Get(string signature,string timestamp,string nonce,string echostr){    
if (CheckSignature.Check(signature, timestamp, nonce, token))    
{        
return Content(echostr);    
}    
else    
{       
return Content("err");    
}
}

[HttpPost][ActionName("Index")]
public ActionResult Get(string signature, string timestamp, string nonce){     
StreamReader sr = new StreamReader(Request.InputStream, Encoding.UTF8);     
XmlDocument doc = new XmlDocument();     
doc.Load(sr);     
sr.Close();     
sr.Dispose();     
WxMessage wxMessage = new WxMessage();     
wxMessage.ToUserName = doc.SelectSingleNode("xml").SelectSingleNode("ToUserName").InnerText;     
wxMessage.FromUserName = doc.SelectSingleNode("xml").SelectSingleNode("FromUserName").InnerText;     
wxMessage.MsgType = doc.SelectSingleNode("xml").SelectSingleNode("MsgType").InnerText;     
wxMessage.CreateTime = int.Parse(doc.SelectSingleNode("xml").SelectSingleNode("CreateTime").InnerText);     
if (wxMessage.MsgType == "event")     
{         
wxMessage.EventName = doc.SelectSingleNode("xml").SelectSingleNode("Event").InnerText;         
if (!string.IsNullOrEmpty(wxMessage.EventName) && wxMessage.EventName == "subscribe")         
{              
string content = "您好，欢迎访问garfieldzf8测试公众平台";              
content = SendTextMessage(wxMessage, content);              
return Content(content);        
}    
}            
return Content("");}private string SendTextMessage(WxMessage wxmessage,string content){      
string result = string.Format(Message, wxmessage.FromUserName,wxmessage.ToUserName,DateTime.Now.Ticks, content);      
return result;} 
public string Message {     
get     
{         
return @"<xml>                      
<ToUserName><![CDATA[{0}]]></ToUserName>                      
<FromUserName><![CDATA[{1}]]></FromUserName>                      
<CreateTime>{2}</CreateTime>                      
<MsgType><![CDATA[text]]></MsgType>                      
<Content><![CDATA[{3}]]></Content>                 
</xml>";            
}    
}

public class WxMessage  
{        
public string ToUserName { get; set; }        
public string FromUserName { get; set; }        
public long CreateTime { get; set; }        
public string Content { get; set; }        
public string MsgType { get; set; }        
public string EventName { get; set; }        
public string EventKey { get; set; }   
}