将复杂对象序列化到mongoDB

Question

I have a few questions that are closely related so I am grouping them under this question.

I'm trying to create a persistent db for my object model using c# and the mongoDB drivers and database. I want to be able to store all of my users objects - inside those users should be sessions (a "list" or similar data structure), and in each session are different events and records that they created (also lists). When a new request is made - initially I look up the user by its identifier. If it exists I create a session object. Add that session object to the user's session list and then make appropriate updates (adding events or records to sessions). (else I create a new user - add it to the db and then do the previous steps)

My problem is that when I do "collection.save(user)" or "find(user)" I am getting errors - can not serialize an abstract class. Per the documentation I should be able to use "auto-mapping" feature so I thought it would work out of the box. That would be great. I would like my db object to appear as just a container for my user objects as is in the UsersDb class.

If not - are there appropriate "mongodb" container classes I can use (ie instead of " List<Session> " use -> BsonList<Session> )? Also how should I go about instantiating containers inside of my classes? If they are generated by the serializer should I initiate them in the constructor? Also how can I store arbitrary "dynamic" data in my classes (just some regular json)

I am creating a basic collection like this:

public class UsersDb 
{
    public UsersDb()
    {
        MongoServerSettings settings =new MongoServerSettings();
        settings.Server = new MongoServerAddress("localhost",27017);
        MongoServer server = new MongoServer(settings);
        MongoDatabase db = server.GetDatabase("defaultDb");
        Users = db.GetCollection<User>("Users");
        //Users.Drop();
    }

    public MongoCollection<User> Users { get; set; }        
}

Here is my user class: already here i have a problem because the constructor needs to be able to create a session list - but what happens if it was serialized by the mongo driver?

public User()
{
    SessionComparer uc = new SessionComparer();
    Sessions = new List<Session>();;
}

public ObjectId Id { get; set; }
public string Udid { get; set; }
public DateTime EnrollDate { get; set; }
public string Email { get; set; }
public string UserName { get; set; }
public string Password { get; set; }
public List<Session> Sessions { get; set; }

My session class

public class Session
{
    public Session()
    {
        Events = new List<Event>();
        Records = new List<Record>();
    }
    public string SessionId { get; set; }
    public DateTime Time { get; set; }
    public dynamic Parameters { get; set; }
    public IList<Event> Events { get; set; }
    public IList<Record> Records { get; set; }
}

Records

public class Record
{
    public Record()
    {
        RecordId = Guid.NewGuid().ToString();
        CreatedAt = DateTime.Now;
    }
    public string Name { get; set; }
    public string RecordId { get; set; }
    public DateTime CreatedAt { get; set; }
    public DateTime Time { get; set; }
    public dynamic Data { get; set; }
}

and the events

public class Record
{
    public Record()
    {
        RecordId = Guid.NewGuid().ToString();
        CreatedAt = DateTime.Now;
    }
    public string Name { get; set; }
    public string RecordId { get; set; }
    public DateTime CreatedAt { get; set; }
    public DateTime Time { get; set; }
    public dynamic Data { get; set; }
}

Answer 1

You cannot de-serialize dynamic. In order to use real classes you need to have something more strict.

Probably following workaround can be suitable:

[BsonKNownTypes(typeof(Implementation1))]
[BsonKNownTypes(typeof(Implementation2))]
public class DynamicModelHere {}
public class Implementation1 : DynamicModelHere { property, property, property }
public class Implementation2 : DynamicModelHere { property, property, property }