将两个linq查询联接到单个查询

Question

I have the following linq queries.. what is the best way to join both of them to a single query.

List<string> consumerids = plays.Where(w => w.playyear == group_period.year 
                                         && w.playmonth == group_period.month 
                                         && w.sixteentile == group_period.group)
                                .Select(c => c.consumerid)
                                .ToList();


int groupcount = plays.Where(w => w.playyear == period.playyear 
                               && w.playmonth == period.playmonth 
                               && w.sixteentile == group 
                               && consumerids.Any(x => x == w.consumerid))
                      .Count();

Please note that the two queries even though have a similar where clause use different values in them (eg. group_period.year and period.playyear )

Answer 1

If these 2 queries do different things, you can keep them separate. It is more readable that way.

What you can do to improve is make these two be executed as 1 query in the database.

All you need to do is remove the ToList() :

You can also have the predicate of the second Where as the predicate of the Count

var consumerids = plays.Where(w => w.playyear == group_period.year &&
                                   w.playmonth == group_period.month &&
                                   w.sixteentile == group_period.group)
                       .Select(c => c.consumerid);

int groupcount = plays.Count(w => w.playyear == period.playyear &&
                                  w.playmonth == period.playmonth &&
                                  w.sixteentile == group &&
                                  consumerids.Any(x => x == w.consumerid));