How to add value to array in MongoDb collection

Question

Took a job recently where they use Mongo. I come from an SQL background. I'm so frustrated with even the basics of Mongo. You're my last resort before I beg to switch.

I have a collection with one document in it. The document currently has two arrays in it, but it will hold many more. I simply want to add a value to either of these arrays. (Using C#)

Is that an update or simply an add? I've not been successful in finding any solution even close to solving this.

The most success I have had so far is returning the entire collection. Like this:

var corrosion = collection.Find(new BsonDocument()).ToList();

I suppose I could create a new JSON file, add my value to it, then try and upload back into mongo, but that seems like way more work then necessary.

Is there a way to take a string value and add that to either of these arrays ?

{"_id":{"$oid":"Random nums and lets"},
"FreeCr":[
  "Add New",
  "4130 ",
  "1008 ",
  "AA70",
  "AA2",
  "AA6",
  "EN9"
],"GalCr":[
  "Add New",
  "AA7 / A286",
  "AAT6 / 316SS",
  "AA / Ti6-4",
  "AA / 4130 Steel",
  "AA / CFRP",
  "AA / A286",
  "AA / Ti6-4",
  "AA / 4130 Steel",
  "AA / Ti6-4",
  "316SS",
  "1008 Steel"
 ]
}

Your help is so very much appreciated.

thewallrus · Accepted Answer · 2022-01-05 20:31:31Z

1

It is more of an update. Mongo still has CRUD operations. Assuming you have a CorrosionModel similiar to this:

public class CorrosionModel
{
    [BsonId]
    [BsonRepresentation(BsonType.ObjectId)]
    public ObjectId Id { get; set; }
    public List<string> FreeCr { get; set; }
    public List<string> GalCr { get; set; }

}

Try this:

List<CorrosionModel> corrosion = collection.Find(new BsonDocument()).ToList(); //get your model

List<string> curList = corrosion[0].FreeCr; //modify your model
curList.Add("NEW VALUE2!");

//update Mongo
var filter = Builders<CorrosionModel>.Filter.Eq("Id", corrosion[0].Id); 
collection.ReplaceOne(filter, corrosion[0], new ReplaceOptions { IsUpsert = true });

answered Jan 5, 2022 at 20:31

thewallrus

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1 Comment

swapmeet_Lou Over a year ago

Thank you. Yes. I did have a corrosion model. Your solution worked perfectly. Grateful and thank you for the assist..

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