Look at the 3 following queries:

var items1 = db.GetCollection<EmailMessage2>().Linq().Where(x => x.Attribs.Count == 2).ToList();
var items2 = db.GetCollection<EmailMessage2>().Find("{ _t: \"EmailMessage2\", Attribs: { $size:

} }").Documents.ToList();
var items3 = db.GetCollection<EmailMessage2>().Linq().Where(x => x.Attribs.Count > 0).ToList();

1 and 2 work fine but 3 brings no result back. I would expect that 3rd query return the same as 2nd (which indeed are the same query).