Question

I have 3 Lists which contains objects of type Book.

Each book has a name and the total amount of that Book.

Is there a way to merge all 3 lists into a new one, where if there are books with the same name in different lists their totals will be added together?

Edit: tried using union and concat but they don’t add the totals together

List<Book> completelist = booklist[0].Concat(booklist[1])
                                     .Concat(booklist[2]).ToList();

Cheers

Answer 1

var merged = list1.Concat(list2).Concat(list3)
    .GroupBy(book => book.Name)
    .Select(g => new Book
    {
        Name = g.Key,
        Total = g.Sum(book => book.Total),
    })
    .ToList();