How to retrive only specific fields form MongoDB using C#

Question

For instance I have a database of cars, which have a field called manufacture.

car: {
     _id: <ObjectId>,
     manufacture: "Opel",
     model: "Astra"
}

How can I get all manufactures without repeating them using the latest implementation official C# driver for MongoDB?

I'd like this to be done in my request to the database, not after.

Which driver are you using to connect to Mongo? Also, how does the data look within Mongo? — Dr Schizo
– Dr Schizo, Commented Oct 2, 2015 at 7:29
@Dr Schizo I use the official driver. The manufacture is a string field of the car entity. — Sasha White
– Sasha White, Commented Oct 2, 2015 at 7:37
can we get an example of what it looks like in Mongo? As what you are requesting we really need to know what the data looks like. — Dr Schizo
– Dr Schizo, Commented Oct 2, 2015 at 7:52

XtremeBytes · Accepted Answer · 2015-10-02 21:05:43Z

5

This should do it

        var db = database.GetCollection<BsonDocument>("cars");

        FieldDefinition<BsonDocument, string> field = "car.manufacture";
        FilterDefinition<BsonDocument> filter = new BsonDocument();

        var a = db.DistinctAsync(field, filter).GetAwaiter().GetResult().ToListAsync().GetAwaiter().GetResult();

edited Oct 2, 2015 at 21:05

answered Oct 2, 2015 at 20:53

XtremeBytes

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Comments

Bhargav Rao · Accepted Answer · 2021-01-15 09:34:37Z

0

Use the Distinct() method: http://api.mongodb.org/csharp/current/html/M_MongoDB_Driver_MongoCollection_Distinct.htm

The field name should be passed as a string, some generic MongoDB examples: http://docs.mongodb.org/manual/reference/method/db.collection.distinct/

Following some examples, it should look like this: var result = await collection.Distinct('manufacture');.

edited Jan 15, 2021 at 9:34

Bhargav Rao

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answered Oct 2, 2015 at 8:24

Shanoor

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3 Comments

Sasha White Over a year ago

I can't find this method in the latest version of MongoDB driver for C#, but DistinctAnsync, which takes different parameters.

Liam Over a year ago

This should be a comment

Daemon Painter Over a year ago

While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes.

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