The request failed with HTTP status 407: Proxy Authentication Required ( The ISA Server requires authorization to fulfill the request. Access to the W

I got this error , it is very amazing for me because sometimes it works and sometimes it throws me error. Actually firewall needs your credentials to verify you so, use this code snippet .

WebProxy wbProxy = new WebProxy();
wbProxy.Credentials = CredentialCache.DefaultCredentials;
objService.Proxy = wbProxy;
It works for me!!