Grupowanie anonimowego typu

 List<Car> myCars = new List<Car>()
            {
                new Car("E250", new Engine(1.8, 204, "CGI"), 2009),
                new Car("E350", new Engine(3.5, 292, "CGI"), 2009),
                new Car("A6", new Engine(2.5, 187, "FSI"), 2012),
                new Car("A6", new Engine(2.8, 220, "FSI"), 2012),
                new Car("A6", new Engine(3.0, 295, "TFSI"), 2012),
                new Car("A6", new Engine(2.0, 175, "TDI"), 2011),
                new Car("A6", new Engine(3.0, 309, "TDI"), 2011),
                new Car("S6", new Engine(4.0, 414, "TFSI"), 2012),
                new Car("S8", new Engine(4.0, 513, "TFSI"), 2012)
            };

            var elements = from car in myCars
                           where car.Model == "A6"
                           select new
                           {
                               engineType = car.Motor.Model == "TDI" ? "diesel" : "petrol",
                               avgHPPL = car.Motor.HorsePower / car.Motor.Displacement
                           }
                           into obj
                           select obj;

var elements = myCars
                .Where(x => x.Model == "A6")
                .Select(x => new
                {
                    engineType = x.Motor.Model == "TDI" ? "diesel" : "petrol",
                    avgHPPL = x.Motor.HorsePower / x.Motor.Displacement
                })
                .GroupBy(x => x.engineType)
                .Select(x => new
                {
                    x.First().engineType,
                    agerage = x.Average(z => z.avgHPPL)
                });