BsonSerializationException when dealing with interfaces

[yaseralnajjar]

How to reproduce:

1. Run the project.
2. Add a car and fill the info.
3. Stop the mongo server.*
4. Run the mongo server and run the project again.
5. Refresh couple of times, and this exception will show:

BsonSerializationException: Unknown discriminator value 'Employee'.
MongoDB.Bson.Serialization.BsonSerializer.LookupActualType(Type nominalType, BsonValue discriminator)

FormatException: An error occurred while deserializing the Owner property of class EFMongoDemo.Web.Models.Car: Unknown discriminator value 'Employee'.
MongoDB.Driver.Linq.MongoQueryProviderImpl.Execute(Expression expression)

This happens on the call:

var cars = await _context.Cars.ToListAsync();

And I noticed there isn't a collection called owner in the db after using the interface.

[crhairr]

Duplicate of #9.

As I said in #13, interfaces aren't really support by EF Core, which is beyond the control of this project.

The only real issue is the navigation property. As I said in #9, navigations aren't fully supported yet, so you won't see that second Owner collection get created just because you added a Car. In the current implementation, Car.Owner will be treated as a subdocument, with the entire graph getting stored in a cars collection. For now, you should refactor your entities to use Car.OwnerId, and add the Owner instance directly to your DbContext, and then use a Join to look them up and project a view model that maps between the Car and Owner:

    _context.Cars
        .Join(_context.Employees,
            car => car.OwnerId,
            employee => employee.Id,
            (car, employee) => new CarAndOwnerModel
            {
                Car = car,
                Owner = employee
            });

I am working through the navigation implementation now, and I hope to have a solution for it soon.