Querying using Lambda Expression for exists within a list

Question

In my project, I need to return a list of car data that does not match the model Id' provided in the array. I'm unsure on how I would go in getting my query to work. So far i have the following below:

var IdList = new List<int> { 60,61,62, 63, 64, 65 };
var query = Context.ManufacturersTable.Where(m => m.Date == date && m.CountryToship = country && m.ExportOnly == false);
if(query.Count() > 0)
    query = query.Where(x => x.CarMoreInfoTable.CarModelTable.Where(f => IdList.Contains(f.ModelId))) //Cannot convert lambda expression to intended delegate type error here

return query

As you can see in the above query I have 3 tables all linked to each other. But please could some direct me on how I would query all data that does not contain the Id's in the given array?

Thank you

try with query.Where(x => x.CarMoreInfoTable.CarModelTable.Any(f => !IdList.Contains(f.ModelId))), Point of contention use usage of inner Where() — Satpal
– Satpal, Commented Jul 12, 2017 at 9:32
if I've understood this correctly, could you do f => !IdList.Contains(f.ModelId)? — Dave Becker
– Dave Becker, Commented Jul 12, 2017 at 9:33
Only just noticed that you put an error message in a comment at the end of a line that is out of view. Might be better to put that message in the body of the post so it can be seen without scroll bars. — Dave Becker
– Dave Becker, Commented Jul 12, 2017 at 9:38
Could you please describe the cardinality of the relationships? — Dave Becker
– Dave Becker, Commented Jul 12, 2017 at 9:49

miszczak · Accepted Answer · 2017-07-12 09:54:49Z

2

You have an error because second 'Where' is the issue here, first Where expects to delegate method return bool instead of IEnumerable. (Comment edit) And I think you have to negate:

IdList.Contains(f.ModelId)

Edit

If you need Car Data (I will assume that it is inside CarModel class) then you need change first Where to SelectMany (we would like to merge many collections into one) and negate the inner expression (with contains).

var result = query
.SelectMany(x => x.CarMoreInfoTable.CarModelTable
                  .Where(f => !IdList.Contains(f.ModelId))).ToList();

edited Jul 12, 2017 at 9:54

answered Jul 12, 2017 at 9:35

miszczak

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2 Comments

Dave Becker Over a year ago

won't that omit all CarModelTable items even if only one of them is in IdList

miszczak Over a year ago

@DaveBecker I Edited my answer

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