检测WebService是否存在

如果不用组件，可以用下列方法：

     public bool IsWebServiceAvaiable(String url)
        {
            try
            {
                HttpWebRequest myHttpWebRequest = (HttpWebRequest)WebRequest.Create(url);
                using(HttpWebResponse myHttpWebResponse = (HttpWebResponse)myHttpWebRequest.GetResponse())
                {
                    return true;
                }
            }
            catch (WebException e)
            {
                if (e.Status == WebExceptionStatus.ProtocolError)
                {
                   XXX.LogMessage(String.Format("Status Code : {0}", ((HttpWebResponse)e.Response).StatusCode));
                    XXXX.LogMessage(String.Format("Status Description : {0}", ((HttpWebResponse)e.Response).StatusDescription));
                }
            }
            catch (Exception e)
            {
              XXX.LogMessage(e.Message);
            }
            return false;
        }