var keywords = query.Split(new char[] {' '}, StringSplitOptions.RemoveEmptyEntries).ToList();

IQueryable<News> searchQuery;
if (categoryId == null)
{
      searchQuery = from n in dbEntities.News.Include("Category")
                    where keywords.Any(w => n.Title.IndexOf(w, StringComparison.InvariantCultureIgnoreCase) > -1)
                    select n;
}
else
{
      searchQuery = from n in dbEntities.News.Include("Category")
                    where n.Category.CategoryId == categoryId &&
                          keywords.Any(w => n.Title.IndexOf(w, StringComparison.InvariantCultureIgnoreCase) > -1)
                    select n;
}

resultPagesCount = (int)(Math.Ceiling(1.0 * searchQuery.Count() / NewsRepository.PAGE_SIZE));