Mongo c# Driver Query (Select subfields)

Question

folowing situation: I have a list of Users, evry one have a field with a List of Comments.

User1: {
      ...
      Id : 'xxxx',
      Comment : [{
                   ...
                   Status : 1
                }
                ,{
                   ...
                   Status : 0
                }]
}

I am looking for a Mongo c# Query that select all Comments with status 1 of all users in the DB Collection.

sry for bad English.

thx

You can't do that in MongoDB directly. It doesn't support returning only matching array elements. It's either only the first match, or all. You'd need to do a filter on the client. — WiredPrairie
– WiredPrairie, Commented Apr 10, 2014 at 16:24

PetarPenev · Accepted Answer · 2014-04-10 15:12:31Z

2

Let's assume you have the following classes that contain the serialized values for your collection:

public class User1
{
    public string Id { get; set; }

    public Comment[] Comments { get; set; }
}

public class Comment
{
   public int Status { get; set; }
}

Then the query should be something like:

var query =
    collection.AsQueryable<User1>().SelectMany(user => user.Comments.Where(com=>com.Status == 1));

answered Apr 10, 2014 at 15:12

PetarPenev

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1 Comment

WiredPrairie Over a year ago

That won't work. SelectMany isn't supported in MongoDB's Official LINQ implementation.

Benjamin Melaoueh · Accepted Answer · 2014-04-11 06:40:46Z

0

thx.

I slove it like this:

var query1  =  Query.EQ("Comments.Status", 1)
IEnumerable<Comment> comments = Collection.Distinct<Comment>("Comments", query1).Where(x => x.Status == 1);

comments .toList() // <= list of Comments with Status 1

if someone has a better solution please post it.

Thx again,

Benjamin

answered Apr 11, 2014 at 6:40

Benjamin Melaoueh

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