c# – Linq-to-SQL何时运行查询？

public class Car
{
    public Guid CarId { get; set; }
    public string Make { get; set; }
    public string Model { get; set; }
    public int HorsePower { get; set; }
}

public class CarRepository
{
    private readonly MyDataContext _dc;

    private readonly Func<DbCar,Car> _mappedCar =
        c => new Car
                 {
                     CarId = c.CarId,HorsePower = c.HorsePower,Make = c.Make,Model = c.Model,};

    public CarRepository(MyDataContext dc)
    {
        _dc = dc;
    }

    public Car GetCar(Guid carId)
    {
        var car = _dc.GetTable<DbCar>()
            .Select(_mappedCar)
            .Single(c => c.CarId == carId);                

        return car;
    }        
}