protected string GetRedirectUrl(RedirectUrlModel redirectModel)
 {
     if (redirectModel != null)
     {
         if (redirectModel.ApplicationPageId.HasValue)
         {
             return(UrlUtility.GetSingleActionUrl("GetAppPageIndex",
                                                  (redirectModel.ListParameter ?? new List <string>()).
                                                  Union(new List <string>()
             {
                 $"applicationPageId={redirectModel.ApplicationPageId}"
             }).ToArray()));
         }
         else
         {
             return(redirectModel.Url);
         }
     }
     else
     {
         return(null);
     }
 }