CODEWITHSUNDEEP
c#mongodblinqnosql
aknuds1
aknuds1

Reputation: 68097

How do I translate this unsupported LINQ query to its native Mongo equivalent?

I have this chained LINQ query which MongoDB fails to execute:

RoleCollection.AsQueryable().Where(r => r.Users.Any(id => id == user.Id))
    .Select(r => r.Name).ToArray();

This results in the following error:

Any is only support for items that serialize into documents. The current serializer is ObjectIdSerializer and must implement IBsonDocumentSerializer for participation in Any queries.

How can I translate the query into a native query which Mongo will support?

Upvotes: 1

Views: 792

Answers (2)

aknuds1
aknuds1

Reputation: 68097

I got the following query working, although I'm not entirely certain as to its semantics yet:

RoleCollection.Find(new QueryDocument("Users", user.Id))
            .Select(r => r.Name).ToArray();

Upvotes: 1

Rudi Visser
Rudi Visser

Reputation: 21989

You should be able to replace .Any() with a combination of .Where() and a length check, like so:

RoleCollection.AsQueryable().Where(r => r.Users.Where(id => id == user.Id).Length > 0)
    .Select(r => r.Name).ToArray();

Note however that there is a performance implication here since it will pull back all of the Users with that id to do a length on it.

I'm not sure what Mongo supports (Sorry I'm answering this purely from a perspective), but you could also use a combination of FirstOrDefault and perform a null check in your where. That might be better since you're only ever expecting one or nothing:

RoleCollection.AsQueryable().Where(r => r.Users.FirstOrDefault(id => id == user.Id) != null)
    .Select(r => r.Name).ToArray();

Upvotes: 1

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