I am looking to get the written text from an internet site with no source code.

I've this code:

HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create("http://www.google.com");
myRequest.Method = "GET";
WebResponse myResponse = myRequest.GetResponse();
StreamReader sr = new StreamReader(myResponse.GetResponseStream(), System.Text.Encoding.UTF8);
string result = sr.ReadToEnd();
sr.Close();
myResponse.Close();
Console.WriteLine(result);

Which obviously can give me the written text but the source code too. How shall I get rid of the origin code?

I would recommend utilizing an HTML parser such as the HTML Agility Pack - when the document is loaded into it you are able to extract the written text in the top node having its InnerText property.