Network Programming in .NET

If you need a quick check to determine the country of origin of your website visitor using Javascript, then you can use this little snippet of code using the ip-api service;

  var s = document.createElement("script");
  s.src = "http://ip-api.com/json/?callback=ipFound";
  document.body.appendChild(s);
  function ipFound(ipInfo)
  {
	  alert("You are from " + ipInfo.countryCode);
  }

It’s free to use (for non-commercial purposes), and uses no API Key, It’s using JSONP which is supported on most browsers.

Evidently, if you want more foolproof check, then a server-side check would be better, but it’s good to help guide your users to the right country, or preselect some options for them.