MongoDB C# driver - serialization of POCO references?

Question

I'm researching MongoDB at the moment. It's my understanding that the official C# driver can perform serialization and deserialization of POCOs. What I haven't found information on yet is how a reference between two objects is serialized. [I'm talking about something that would be represented as two seperate documents, with ID links, rather than embeded documents.

Can the serialization mechanism handle this kind of situation? (1):

class Thing {
    Guid Id {get; set;}
    string Name {get; set;}
    Thing RelatedThing {get; set;}
}

Or do we have to sacrifice some OOP, and do something like this? (2) :

class Thing {
    Guid Id {get; set;}
    string Name {get; set;}
    Guid RelatedThing_ID {get; set;}
}

UPDATE:

Just a couple of related questions then...

a) If the serializer is able to handle situation (1). What is an example of how to do this without using embedding?

b) If using embedding, would it be possible to query across all 'Things' regardless of whether they were 'parents' or embedded elements? How would such a query look like?

Answer 1

The C# driver can handle serializing the class containing a reference to another instance of itself (1). However:

1. As you surmised, it will use embedding to represent this
2. There must be no circular paths in the object graph or a stack overflow will occur

If you want to store it as separate documents you will have to use your second class (2) and do multiple inserts.

Querying across multiple levels is not really possible when the object is stored as one large document with nested embedding. You might want to look at some alternatives like:

https://docs.mongodb.com/manual/applications/data-models-tree-structures/