Linq To Entities – how to filter on child entities

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There is no “nice” way of doing this, but you could try this – project both, Group and filtered Users onto an anonymous object, and then Select just the Groups:

var resultObjectList = AllGroups.
                       Select(g => new
                               {
                                   GroupItem = g,
                                   UserItems = g.Users.Where(u => !u.IsInactive)
                               }).ToList();

FilteredGroups = resultObjectList.Select(i => i.GroupItem).ToList();

This isn’t a documented feature and has to do with the way EF constructs SQL queries – in this case it should filter out the child collection, so your FilteredGroups list will only contain active users.

If this works, you can try merging the code:

FilteredGroups = AllGroups.
                 Select(g => new
                               {
                                   GroupItem = g,
                                   UserItems = g.Users.Where(u => !u.IsInactive)
                               }).
                 Select(r => r.GroupItem).
                 ToList();

(This is untested and the outcome depends on how EF will process the second Select, so it would be nice if you let us know which method works after you’ve tried it).

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