check the request of url and send response data to that url using xml

The request is not clear and does not seem to makes much sense. Here is why: there is no such thing as "request from URL". In general case, you simply don't have the "URL" to which you can send anything; it assumes that there is a host exposed to Web and running some service supporting one of the standard Web protocols, such as HTTP, FTP, and the like. Normally, the request comes from the host and software (for example, most typical, a Web browser) where there is no such thing.

You can get some user sending you an HTTP request from the instance of the class, not too surprisingly, System.Web.HttpRequest:
http://msdn.microsoft.com/en-us/library/system.web.httprequest%28v=vs.110%29.aspx[^],
http://msdn.microsoft.com/en-us/library/system.web.httprequest.urlreferrer(v=vs.110).aspx[^],
http://msdn.microsoft.com/en-us/library/system.web.httprequest.useragent(v=vs.110).aspx[^],
http://msdn.microsoft.com/en-us/library/system.web.httprequest.userhostaddress(v=vs.110).aspx[^],
http://msdn.microsoft.com/en-us/library/system.web.httprequest.userhostname(v=vs.110).aspx[^].

Note that even, for example, the host address is provided, it does not mean that you can send your request using that address. :-)

—SA