Find Pages With Criteria of type T Example Episerver 7,8,9

  private IEnumerable<T> FindPagesByPageTypeRecursively<T>() where T : IContent  
     {  
       var criteria = new PropertyCriteriaCollection  
       {  
         new PropertyCriteria  
         {  
            Name = "PageTypeID", Type = PropertyDataType.PageType, Value = typeof(T).GetPageTypeId().ToString(), Required = true  
         }  
       };  
       IEnumerable<T> descendants = DataFactory.Instance.FindPagesWithCriteria(PageReference.RootPage,  
                                           criteria).Cast<T>();  
       return descendants;  
     }