The question is how to construct HttpWebRequest
so queried server will think it comes from a browser?
You could set the User-Agent HTTP request header.
var request = (HttpWebRequest)WebRequest.Create("http://www.google.com");
request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.2 (KHTML, like Gecko) Chrome/15.0.874.121 Safari/535.2";
or if you work with a WebClient:
using (var client = new WebClient())
{
client.Headers[HttpRequestHeader.UserAgent] = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.2 (KHTML, like Gecko) Chrome/15.0.874.121 Safari/535.2";
...
}