Try this code .
string ProxyServer = null;
string ProxyUser = null;
string ProxyPass = null;
string ProxyPort = null;
ProxyServer = "00.00.00.00";
ProxyUser = "abc";
ProxyPass = "xyz";
ProxyPort = "8080";
string url = "http://.........";
WebRequest req = WebRequest.Create(url);
req.Proxy = WebProxy.GetDefaultProxy();
req.Proxy.Credentials = CredentialCache.DefaultCredentials;
WebResponse resp = req.GetResponse();
System.IO.StreamReader textReader = new System.IO.StreamReader(resp.GetResponseStream());
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