public static string GetSearchVacantRecord(string columnname, ICollection <QueryCondition> lstCondition, ICollection <QueryCondition> vacantCond)
 {
     try
     {
         QueryDesigner objQuery = new QueryDesigner();
         return(JsonConvert.SerializeObject(objQuery.GetDynamicVacantRecord(lstCondition, columnname, vacantCond)));
     }
     catch (Exception ex)
     {
         return(null);
     }
 }