Add a reference to another document in MongoDB C# MongoDB.Driver - mongodb

Question

I have two classes:
public class MDBProducts
{
public string _id { get; set; }
public string order_number { get; set; }
[BsonIgnoreIfNull]
public List<Classes.MDBParts[]> partsId { get; set; }
}
public class MDBParts
{
public string _id { get; set; }
public string accountCode { get; set; }
}
With this lookup command mongodb embedded whole document information.
string param = "{$lookup: { from: 'Parts',localField: 'order_number',foreignField: 'accountCode',as:'partsId'} }";
BsonDocument document = BsonDocument.Parse(param);
var pipeline = new[] { document };
var result = Classes.MdB.connectDbProducts().Aggregate<MDBProducts>(pipeline).ToList();
I want to add to "partsId" only MDBParts class _id field. May you help me notice, how to do that?

Answer 1

References between Parts and Products collections
`var lookup1 = new BsonDocument
{
{
"$lookup",
new BsonDocument
{
{ "from", "Parts" },
{ "localField", "order_number" },
{ "foreignField", "productNumber" },
{ "as", "partsId" }
}
},
};
var lookup2 = new BsonDocument
{
{
"$project",
new BsonDocument
{
{ "partsId", "$partsId._id" },
{ "id", 1 }
}
}
};
var pipeline = new[] { lookup1, lookup2 };
var result = connectDbProducts().Aggregate<Products>(pipeline).ToList();
foreach (var item in result)
{
if (item.partsId.Count != 0)
{
var filterID = Builders<Products>.Filter.Eq(x => x._id, item._id);
var setTableTop = Builders<Products>.Update.Set(x => x.partsId, item.partsId);
connectDbProducts().UpdateOne(filterID, setTableTop);
}
else
{
var filterID = Builders<Products>.Filter.Eq(x => x._id, item._id);
var setTableTop = Builders<Products>.Update.Unset(x => x.partsId);
connectDbProducts().UpdateOne(filterID, setTableTop);
}
}`
Products Class
public class Products
{
public object _id { get; set; }
public string electricity_based_on { get; set; }
public double? full_price { get; set; }
public DateTime manufacturing_date { get; set; }
public string order_code { get; set; }
public string order_comment_names { get; set; }
public string order_name { get; set; }
public string order_number { get; set; }
public double? order_quantity { get; set; }
public double? unit_price { get; set; }
[BsonIgnoreIfNull]
public string user_name { get; set; }
[BsonIgnoreIfNull]
public DateTime user_checkTime { get; set; }
[BsonIgnoreIfNull]
public object order_comments { get; set; }
[BsonIgnoreIfNull]
public string tabletop_letter { get; set; }
[BsonIgnoreIfNull]
public string sub_3_4 { get; set; }
[BsonIgnoreIfNull]
public List<string> partsId { get; set; }
}
Connection to DB
public static IMongoCollection<Products> connectDbProducts()
{
try
{
MongoClient dbClient = new MongoClient(Properties.Resource1.mongoDB);
var db = dbClient.GetDatabase("Manufacturing");
var collection = db.GetCollection<Products>("Products");
return collection;
}
catch (Exception toMongoDBParts)
{
WriteLogFile("--MongoDB connection to Parts collection--", toMongoDBParts.StackTrace, toMongoDBParts.Message);
throw;
}
}