Migration: How to Migrate Transformers from 3.x

public class Orders_Total : AbstractTransformerCreationTask<Order>
{
    public class Result
    {
        public double Total { get; set; }
    }

    public Orders_Total()
    {
        TransformResults = orders => 
            from o in orders
            select new
            {
                Total = o.Lines.Sum(l => l.PricePerUnit * l.Quantity)
            };
    }
}

List<Orders_Total.Result> results = session
    .Query<Order>()
    .TransformWith<Orders_Total, Orders_Total.Result>()
    .ToList();

var results = session
    .Query<Order>()
    .Select(x => new
    {
        Total = x.Lines.Sum(l => l.PricePerUnit * l.Quantity),
    })
    .ToList();