linq-在多个列表中的列表中查找项目

Question

I have a highly nested class, and trying to find a single item buried deep within. The following gives me an error "Can't convert type match to bool', although I don't see why it thinks I'm trying to return a boolean.

var match = community.TeamLeagues
   .Where(x => x.Seasons
       .Where(y => y.Divisions
           .Where(z => z.Matches
               .Where(a => a.Id == "1234").FirstOrDefault())));

Answer 1

Where by itself returns a (deferred) enumerable of items and cannot as such be used as a condition by the outer Where . What you probably want to do is to use Contains() , Any() or All() inside the outer Where s that will return the result you're looking for.

Something like this might be what you're after:

var match = community.TeamLeagues.Where(t =>
        t.Seasons.Any(
        s => s.Divisions.Any(
        d => d.Matches.Any(
        m => m.Id == "1234")
        )));

Answer 2

The Where method needs to evaluate an expression that returns a bool . Your nested Where s are not doing that - the only Where that is, is the last one a => a.Id == "1234" , all the other expressions are returning an IEnumerable .

Answer 3

z.Matches.Where(a => a.Id == "1234").FirstOrDefault() returns a object of type Match (your collection item type of the IEnumerable Matches ) (or null), no boolean value. I guess you need to check if there are entires in matches that have a Id 1234. Use Any to evaluate a condition:

var match = community.TeamLeagues.Where(x => 
              x.Seasons.Any(y => 
                y.Divisions.Any(z => 
                   z.Matches.Any(a => a.Id == "1234")
            )));

[ items.Where(x => x.Id == 4).Any() is the same as items.Any(x => x.Id == 4) ]

This returns you all TeamLeagues which contain a Season which contain a Division which contain a Match which has a element with the id 1234.

Answer 4

To make it simple you can also use the Matches table directly and using a ViewModel you can represent your view.

like: var MyViewModel = (from l in Mathes where l.Id == "1234" select new MyViewModel { Id = l.Id, MatchName = l.Name, }).ToList();

Answer 5

Couldn't get it working with linq, but works with query syntax.

var leagueMatch = (from teamLeague in community.TeamLeagues
                from season in teamLeague.Seasons
                from division in season.Divisions
                from match in division.Matches.Where(x => x.Id == "1234")
                select match).FirstOrDefault();