How can i fix this mongo c# find by Id to return result other than null?

Question

I am trying to return a single value from a collection in my MongoDB database, however I am getting a null value returned and a document with that id exists in the collection.

    public async Task<Business> GetBusiness(string businessId)
    {
        var objectId = new ObjectId(businessId);
        var filter = Builders<Business>.Filter.Eq("_id", objectId);
        var entity = await _businessMongoCollection.Find(filter).FirstAsync();
        return entity;
    }

I have also tried doing it this way but i get a null result.

var filter = Builders<Business>.Filter.Eq("_id", new ObjectId(businessId));
var foundBusinessTask = await _businessMongoCollection.FindAsync(filter);
var foundBusiness = await foundBusinessTask.SingleOrDefaultAsync();

Can you show us one of the documents in your collection from the mongo console? `db.your_collection.findOne()` — Kevin Smith, Jun 06 '20 at 14:51

score 0 · Answer 1 · answered Jun 05 '20 at 10:02

0

Could you not use the property specifier instead of the string "_id", like so:

var filter = Builders<Business>.Filter.Eq(b => b.Id, businessId);

I don't think you need to turn the id's into ObjectId

answered Jun 05 '20 at 10:02

Sachin

106
1
4

two issue with this, i'd have to ToString the b.Id like this var filter = Builders.Filter.Eq(b => b.Id.ToString(), businessId); and the second issue is that it still returns null – floormind Jun 05 '20 at 10:11
I am assuming that the Id property is of Guid type in your `Business` class. In which case you should not be passing that parameter `businessId` as string but Guid so the equality check in the filter as I have suggested will be comparing Guid to Guid. No `.ToString()` needed, although you might need `Guid.Parse(businessId)` – Sachin Jun 05 '20 at 16:27

How can i fix this mongo c# find by Id to return result other than null?

1 Answers1