First This Piece of Code will Send a request for given URL.
and will get the response for that request. the Response object will return a data in the form of stream and this code will read the strean data With the help of StreamReader and then write that data into a string.
Uri uri = new Uri("http://www.google.co.in");
//Create the request object
HttpWebRequest req = (HttpWebRequest)WebRequest.Create(uri);
req.UserAgent = "Get Content";
WebResponse resp = req.GetResponse();
Stream stream = resp.GetResponseStream();
StreamReader sr = new StreamReader(stream);
string s = sr.ReadToEnd();