C# how to catch Exeption : I am new in `C#` programming and I don't understand this problem.

                        using (WebClient wc = new WebClient())
                        {   
                           try{
                                wc.Headers[HttpRequestHeader.ContentType] = "application/x-www-form-urlencoded";
                                HtmlResult = wc.UploadString(URI, myParameters);
                            }catch(AuthenticateExeption a){
                                throw new AuthenticateExeption("I can not connect to the server...");
                            }
                        }

I am trying `catch` exeption using my `AuthenticateExeption`, but code never go to `throw new AuthenticateExeption("I can not connect to the server...");` and program always down on `HtmlResult = wc.UploadString(URI, myParameters);` line.

Why?


