/// <summary>
 /// Override this method to inject custom logic when an item is filtered.
 /// </summary>
 /// <param name="item">The item being filtered.</param>
 /// <returns></returns>
 protected sealed override bool OnItemFilter(VirtualPagingItemViewModel <TItem, TModel> item)
 {
     return(true);
 }
 /// <summary>
 /// Override this method to inject custom logic when an item is filtered.
 /// </summary>
 /// <param name="item">The item being filtered.</param>
 /// <returns></returns>
 protected sealed override bool OnItemFilter(VirtualPagingItemViewModel <TItem, TModel> item)
 {
     throw new NotImplementedException();
 }