Execute this query, gives the following exception: ``` statelessSession.Query<Sale>() .Select(x => new SaleDto { Id = x.Id, SaleDate = x.ListChildren.Max(y => y.Date) }) .Where(x => x.SaleDate <= DateTime.Today && x.SaleDate >= DateTime.Today) .ToList(); ``` Exception: `System.ArgumentException: Item with Same Key has already been added.`