Linq Group By On Two Properties That maybe different or the same

Question

I would like to do a group by on two properties who at 95% of the time will be the same, but sometimes it may not by

class Game { string AwayTeamPoolId; // 122 string HomeTeamPoolId; // 144 }

I would like to group all games from the same pool from a list of games. As I mentioned above most of the time this value will be the same for both away/home teams. However there might be a cross pool play game where the values are different. With Linq how can I group say the game by having the awayteampoolid with the group 122, and have hometeampoolid grouped with 144? It's easy if they are the same but different Im not sure.

122 Game 1 (122/122) Game 2 (122/144) 144 Game 2 (122/144) Game 3 (144/144)

Are you saying you want a single item to [possibly] appear in 2 places, ie once for [and 'under'] each distinct PoolId? — tolanj
– tolanj, Commented Oct 27, 2014 at 13:47

Aducci · Accepted Answer · 2014-10-27 13:52:47Z

You need to Concat (union all) the list of AwayTeamPool and HomeTeamPool and then group on that like this:

var query = games.Select(x => new { Game=x, PoolId = x.AwayTeamPoolId }) .Concat(games.Where(x => x.HomeTeamPoolId != x.AwayTeamPoolId) .Select(x=> new { Game=x, PoolId = x.HomeTeamPoolId }) .GroupBy(x => x.PoolId, x => x.Game);

dcastro · Accepted Answer · 2014-10-27 13:34:31Z

1

You can use Enumerable.GroupBy combined with anonymous types.

var groupedGames = games.GroupBy( game => new { game.AwayTeamPoolId, game.HomeTeamPoolId });

To get the games where AwayTeamPoolId is 122 and HomeTeamPoolId is 144:

var games = groupedGames.Single( group => group.Key.AwayTeamPoolId = 122 && group.Key.HomeTeamPoolId = 144)

edited Oct 27, 2014 at 13:34

answered Oct 27, 2014 at 13:22

dcastro

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4 Comments

Mike Flynn Over a year ago

But wouldnt that create a group that contains 122 and 144? I want all games with 122 together (even if the home team has 144) and vice versa.

dcastro Over a year ago

@MikeFlynn It'll create a group for each possible combination of AwayTeamPoolId+HomeTeamPoolId. If for some reason this is not what you want, please provide sample input and expected output so we can help you out.

Mike Flynn Over a year ago

Didnt I do that above?

dcastro Over a year ago

@MikeFlynn I think I understand now, and I think Aducci nailed it.

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