How to compose the linq query with lambda

Question

User1183902823 posted

how to convert the below one with lambda?

if author name is empty then author filter will not be applied rather all author will be return. tell me how could i convert it with lambda?

IQueryable<Book> results = from o in _context.Books
                          orderby o.Id
                          select o;
            if (!string.IsNullOrEmpty(author))
            {
                results = results.Where(t => t.Authers.Contains(author));
            }

Answer 1

User2103319870 posted

tridip1974

if author name is empty then author filter will not be applied rather all author will be return. tell me how could i convert it with lambda

You can try with below query. Logic is OR(||) operator will not check the second condition if first condition satisfies, so you will get all results. If value is not null then second condition will evaluates then you will results which contains the author name

 results = results.Where(t => (author == null || t.Authers.Contains(author)));

Answer 2

User2103319870 posted

IQueryable<Book> results = from o in _context.Books orderby o.Id select o; if (!string.IsNullOrEmpty(author)) { results = results.Where(t => t.Authers.Contains(author)); }

You can also combine both queries like below

            List<Book> results = _context.Books
                                 .Where(t => (author == null || t.Authers.Contains(author)))
                                 .OrderBy(i => i.Id).ToList();