xxxx

WebClient MyWebClient = new WebClient();
//MyWebClient.Proxy = null;
//MyWebClient.Credentials = CredentialCache.DefaultCredentials;//获取或设置用于向Internet资源的请求进行身份验证的网络凭据
IWebProxy proxy = WebRequest.GetSystemWebProxy();
proxy.Credentials = CredentialCache.DefaultCredentials;
MyWebClient.Proxy = proxy;