Get distinct nested document values from a collection in MongoDB using C#

Question

This question involves getting distinct values of a nested document in Mongo DB using C#. I have a collection of documents, each document having the structure:

{
   key1: value1,
   key2: value2,
   key3: {
      nestedKey1: nestedValue1,
      nestedKey1: nestedValue1
   }
}

I need to query a list of distinct nestedKey1 values based on the value of key1. I can do this (using a shell in Robomongo) by using the command:

db.runCommand({distinct:'collection_name', key:'key3.nestedKey1', query: {key1: 'some_value'}})

But how do I achieve this in C# (tutorial here)

@Veeram How do I specify the key key3.nestedKey1 in this case? and not to forget the filter which has to be key1: 'some_value' — Dame Lyngdoh
– Dame Lyngdoh, Commented Jun 30, 2017 at 17:03

s7vr · Accepted Answer · 2017-12-08 14:02:26Z

2

You can try the below distinct query.

IMongoClient mongo = new MongoClient();
IMongoDatabase db = mongo.GetDatabase("databasename");
IMongoCollection<BsonDocument> collection = db.GetCollection<BsonDocument>("collectionname");

BsonDocument filter = new BsonDocument("key1", "some_value");
IList<BsonDocument> distinct = collection.Distinct<BsonDocument>("key3.nestedKey1", filter).ToList<BsonDocument>();

Filter Builder Variant

var builder = Builders<YourClass>.Filter;
var filter = builder.Eq(item => item.key1, "some_value");
IList<string> distinct = collection.Distinct<string>("key3.nestedKey1", filter).ToList<string>();

Field Builder Variant

var builder = Builders<YourClass>.Filter;
var filter = builder.Eq(item => item.key1, "some_value");
FieldDefinition<YourClass, string> field = "key3.nestedKey1";
IList<string> distinct = collection.Distinct<string>(field", filter).ToList<string>();

edited Dec 8, 2017 at 14:02

answered Jul 3, 2017 at 11:59

s7vr

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1 Comment

Dame Lyngdoh Over a year ago

I found the solution. And it is very similar to your answer. Thanks

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