CODEWITHSUNDEEP
c#mongodb
Xavier W.
Xavier W.

Reputation: 1360

MongoDb count subarray elements in C# return all time 0

I have a document in my MongoDb database, and I want to write a query to retrieve documents whose array size is greater than 0 (array is not null or empty to be clear).

Here is my C# code givent the fact that Quotes is my subarray :

internal bool HasQuote(string projectNumber)
{
    var filter = Builders<Entity.Project>.Filter.Eq(x => x.ProjectNumber, projectNumber);
    filter &= Builders<Entity.Project>.Filter.Exists(x => x.Quotes);
    filter &= Builders<Entity.Project>.Filter.SizeGt(x => x.Quotes.Count, 0);

    var res = _mongoCollection.CountDocuments(filter);
    return res > 0;
}

Unfortunately the function returns all time false. It must be related to the SizeGt part, because when I remove this line it is working fine. I tryed other stuff like filter &= Builders<Entity.Project>.Filter.Where(x => x.Quotes.Count > 0); or filter &= Builders<Entity.Project>.Filter.Exists(x => x.Quotes[0]);

Upvotes: 0

Views: 949

Answers (1)

Jawad
Jawad

Reputation: 11364

What does SizeGT takes in as parameters?

SizeGt(FieldDefinition<TDocument> field, int size);

which means you have to provide a Field that you need to get a count on.

What to do to fix your code

Change the line:

filter &= Builders<Entity.Project>.Filter.SizeGt(x => x.Quotes.Count, 0);

to this

filter &= Builders<Entity.Project>.Filter.SizeGt(x => x.Quotes, 0);

Reason you dont provide the Count is because SizeGT knows how to Convert x.Quotes and get a count of it. If you do a count and catch the error, you'll get the error:

Unable to determine the serialization information for x => Convert(x.Quotes.Count).

I just ran the code above on my list and it came back with correct numbers.

Upvotes: 1

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