/// <summary>
 /// Validate the specified username and password
 /// </summary>
 public override void Validate(string userName, string password)
 {
     try
     {
         this.m_traceSource.TraceInformation("Entering OAuth2.Wcf.ClientCredentialValidator");
         IApplicationIdentityProviderService clientIdentityService = ApplicationContext.Current.GetService <IApplicationIdentityProviderService>();
         // attempt to validate
         var auth = clientIdentityService.Authenticate(userName, password);
         if (auth == null)
         {
             throw new FaultException("Non-valid client");
         }
     }
     catch (Exception e)
     {
         this.m_traceSource.TraceEvent(TraceEventType.Error, e.HResult, e.ToString());
         throw;
     }
 }