public interface IDataObject {
  int ID: string;
  // more properties and functions
}

public interface IQueryResult : IReadOnlyList<IDataObject>
{
    int Length { get; }
}

public sealed class QueryResult : IQueryResult
{
    private readonly IReadOnlyList<IDataObject> _list;

    public int Count => _list.Count;

    [ScriptMember("length")]
    public int Length => Count;

    public IDataObject this[int index] => _list[index];

    public QueryResult() => _list = ImmutableArray<IDataObject>.Empty;

    public QueryResult(IEnumerable<IDataObject> items) => _list = items.ToImmutableArray();

    public IEnumerator<IDataObject> GetEnumerator() => _list.GetEnumerator();

    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
}