public class MyService : xxx服务类
    {
        public MyService(string url)
        {
            Url = url;
        }

        protected override WebRequest GetWebRequest(Uri uri)
        {
            HttpWebRequest request = (HttpWebRequest)base.GetWebRequest(uri);
            if (PreAuthenticate)//使用时，必须设置服务类的PreAuthenticate属性为true并设置Credentials属性
            {
                NetworkCredential networkcredential = base.Credentials.GetCredential(uri, "Basic");
                if (networkcredential != null)
                {
                    Byte[] credentialBuffer = new UTF8Encoding().GetBytes(networkcredential.UserName + ":" + networkcredential.Password);
                    request.Headers["Authorization"] = "Basic " + Convert.ToBase64String(credentialBuffer);
                }
                else
                    throw new ApplicationException("No network credentials");
            }
            return request;
        }
    }