使用linq从列表数据中选择

Question

One Book has list of Tag objects. Using linq I want to select list of books where any tag name contains specified filter.

string genre; // filter
List<Book> books = repository.GetBooks();

foreach(Book book in books.Where(x=>x.Tags.Any())) //I'm stuck here

Answer 1

you need to see if any tag name is equal to the filter:

books.Where(book => book.Tags.Any(tag => tag == genre))

or use Contains method:

books.Where(book => book.Tags.Contains(genre))

assuming Tags property returns a sequence of string . If Tag is a user-defined object, use:

books.Where(book => book.Tags.Any(tag => tag.Name == genre))

Answer 2

Something like this should work

var results = books.Where(x => x.Tags.Any(t => t.Name == genre))

Or this:

var results = books.Where(x => x.Tags.Select(t => t.Name).Contains(genre))

Answer 3

尝试以下方法

foreach(Book book in books.Where(x=>x.Tags.Any(t => t.Name == "tag-name"))) 

Answer 4

If Book.Tags is a collection of Tag objects, you should use Any and pass lambda expression:

foreach(Book book in books.Where(x=>x.Tags.Any(t => t.Name == filter)))

If Book.Tags is a collection of string s, you should use Contains method:

foreach(Book book in books.Where(x=>x.Tags.Contains(filter)))