public async Task <IActionResult> OnGetAsync(string categoryName, int pageNumber) { var productList = await _catalogApi.GetCatalog(); CategoryList = productList.Select(p => p.Category).Distinct(); if (!string.IsNullOrWhiteSpace(categoryName)) { ProductList = productList.Where(p => p.Category == categoryName); SelectedCategory = categoryName; } else if (pageNumber > 0) { ProductList = await _catalogApi.GetProductByPage(pageNumber); } else { ProductList = productList; } return(Page()); }