Question

I have a mongo document that contains an array of embedded documents. The embedded documents have a property named “Id”.

{ Name: "Outer object", Embedded: [ {Name: "Embedded A", Id: "5f1c591a71dc237199eeaeda"} ] }

My C# mapping objects look something like this (a simplification, obviously)

public class Outer
{
    public string Name { get; set; }
    public IEnumerable<Inner> Inners { get; set; }
}

public class Inner
{
    public string Name { get; set; }
    public string Id { get; set; }
}

When I write an outer to the database, the C# driver changes the name of the Inner.Id property to _id. How do I circumvent this automatic rename? I’ve tried using the [BsonElement(“Id”)] attribute on the Id property, but it didn’t help.

Answer 1

MongoDB documentation explicitly states:

Documents in MongoDB are required to have a key, _id, which uniquely identifies them.

On the other hand, C# properties are usually pascal-case and don’t use prefixes so driver designers apparently decided to force mapping Id property to _id database attribute.

If you want to bind a non-_id attribute that just happens to be called Id in MongoDB, you could declare another C# property with a name other than Id so the driver doesn’t interfere with it:

public class Inner
{
    public string Name { get; set; }

    [BsonElement("Id")]
    public string IdStr { get; set; }
}