using MongoDB.Bson.Serialization.Attributes;


[BsonIgnoreExtraElements]
public class User
{
     public User()
    {
        Version = Guid.NewGuid();
    }
    [BsonId]
    public Guid Id { get; set; }
    public Guid Version { get; set; }
     public string FirstName { get; set; }
     public Address address { get; set; } // can be null
}

public class Address
{
    public string Street { get; set; }
    public string City { get; set; }
    public string State { get; set; }
}

 User user = new User();
 user.FirstName= "Scott";
 // add user to context
 _context.User.Add(user);
 // save changes
 _context.SaveChanges();

 // read user
* // throws exception as unable to cast null to address*
 var item = _context.User.FirstOrDefault(x => x.FirstName == "Scott");

public class MongoDBContext : DbContext
{
    public DbSet<User> User { get; init; }

    public static MongoDBContext Create(IMongoDatabase database) =>
        new(new DbContextOptionsBuilder<MongoDBContext>()
            .UseMongoDB(database.Client, database.DatabaseNamespace.DatabaseName)
            .Options);

    public MongoDBContext(DbContextOptions options)
        : base(options)
    {

    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {

        base.OnModelCreating(modelBuilder);
        modelBuilder.Entity<User>().ToCollection("user");
    }

    protected override void ConfigureConventions(ModelConfigurationBuilder configurationBuilder)
    {
        configurationBuilder.Conventions.Add(d =>
        new CamelCasePropertyNameConvention(d.GetService<ProviderConventionSetBuilderDependencies>()!));
        base.ConfigureConventions(configurationBuilder);
    }
}