jquery cross-domain requests and. NET background cross-domain requests

The season for the annual train ticket has come again, as a programmer, in the study of the interfaces provided by 12306, encountered some cross-domain issues. Take the query for the remainder of the ticket interface as an example.
The first method:
$.ajax ({
URL: ' Https://kyfw.12306.cn/otn/leftTicket/queryT?leftTicketDTO.train_date=2015-02-05&leftTicketDTO.from_ Station=szh&leftticketdto.to_station=shh&purpose_codes=adult ',
Data: [],
DataType: ' Jsonp ',
Type: ' GET ',
Cache:false,
Async:false,
JSONP: "Callback",//pass to the request handler or page, to obtain the name of the JSONP callback function name (default: Callback)
Jsonpcallback: "Success_jsonpcallback",
Error:function (e) {
Debugger;
$ ("#show"). empty ();
$ ("#show"). Append (e);
                },
success:function (data) {
Debugger;
$ ("#show"). empty ();
$ ("#show"). Append (data);
                }
            });
function Success_jsonpcallback (backdata) {

} 
the requirement for data to be requested across domains in the JSONP format is that the client and server side should have a contractual format. Because we do not know the agreed format of 12306, there is a scene when we request data in this way.

Because the name of the callback function is overridden in a JSONP request. This value is used instead of "callback=?" This get or POST request in the URL parameter in the "Callback" section, because we do not know the name of the 12306 Convention callback parameter, so the URL syntax error.

The second method:

var data = {"Leftticketdto.train_date": "2015-02-05", "leftticketdto.from_station": "Szh", "            Leftticketdto.to_station ":" SHH "," purpose_codes ":" Adult "}; $.getjson ("https://kyfw.12306.cn/otn/leftTicket/queryT?callback=", data, function (backdata) {                 Debugger;                     //Actually the function returned in the background has been replaced with this function, so backdata   //is a JSON object that you've sent back from the background.                            alert (backdata); }); the $.getjson () method is actually the simple version of the first method, which supports cross-domain. Third method:. NET background
String URL = "Https://kyfw.12306.cn/otn/leftTicket/queryT";

/* cross-domain request the first method */
byte[] param = System.Text.Encoding.ASCII.GetBytes ("Leftticketdto.train_date=2015-02-05&leftticketdto.from_ Station=szh&leftticketdto.to_station=shh&purpose_codes=adult ");
HttpWebRequest req = (HttpWebRequest) httpwebrequest.create (URL);
Req. Method = "POST";
Req. Contenttype= "application/x-www-form-urlencoded";
Req. ContentLength = param. Length;
Stream Reqstream = req. GetRequestStream ();
Reqstream.write (Param,0,param. Length);
Reqstream.close ();
HttpWebResponse response = (HttpWebResponse) req. GetResponse ();
StreamReader reader = new StreamReader (response. GetResponseStream (), encoding.getencoding ("GB2312"));
String content = Reader. ReadToEnd ();
Reader. Close ();
Response. Close ();
The Fourth method:System.Net.WebClien T wcient = new System.Net.WebClient (); wCient.Headers.Add ("Content-type", "application/x-www-form-urlencoded"); byte[] PostData = System.Text.Encoding.ASCII.GetBytes ("id=" + Urlargs);byte[] ResponseData = Wcient.uploaddata (URL, "POST", postdata);string returnstr = System.Text.Encoding.UTF8.GetString (responsedata);//Returns the accepted datacontext. Response.ContentType = "Text/plain"; Context.  Response.Write (RETURNSTR);

jquery cross-domain requests and. NET background cross-domain requests