Simple data example with parent document and enumerable child document:

{{public class TestData {
public Guid Id

{ get; set; }

[BsonIgnoreIfNull]
public IEnumerable<TestChildData>? ChildData { get; set; }

}

public class TestChildData {
public Guid Id

{ get; set; }

}

protected override void OnModelCreating(ModelBuilder modelBuilder)

{ base.OnModelCreating(modelBuilder); modelBuilder .Entity<TestData>() .ToCollection(_config.Value.CollectionName) .OwnsMany(x => x.ChildData); }

}}

If ChildData is null in the database, simply trying to ToList() the {{DbSet }}results in an exception:

var data = _dbContext?.TestData.ToList();

System.InvalidCastException: Unable to cast object of type 'MongoDB.Bson.BsonNull' to type 'MongoDB.Bson.BsonArray'.
at lambda_method17(Closure, QueryContext, BsonDocument)
at MongoDB.EntityFrameworkCore.Query.QueryingEnumerable`2.Enumerator.MoveNextHelper()
at MongoDB.EntityFrameworkCore.Query.QueryingEnumerable`2.Enumerator.MoveNext()
at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)

Likely related to EF-99 and EF-63. This is very basic functionality that should be supported without so many problems.