Extracting web content will return unicode characters. why this is happening

For example I used this code:

HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create("http://www.tsetmc.com/Loader.aspx?ParTree=15");
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.ToString());

and some of other types of code but they return bad symbols. And also I used webbrowser control in c# to navigate the site, which is written by asp, but it couldn't browse the website!!