使用LINQ为集合中的所有对象的属性赋值的最佳方法

Question

I have a Car object with a ResaleValue property, and I have a collection of these car objects stored in:

 IEnumerable<Car>

I also have a ResaleCalculator() with a calculate method.

Is there a way in linq to apply a calculation and set the ResaleValue property of every object in the collection without a loop?

Answer 1

You don't really want to use LINQ for this. Firstly, you're not avoiding a loop, you are merely abstracting it away. Secondly, LINQ methods are intended to filter and/or project a sequence, not mutate it. While you could use the .ForEach instance method on List<T> to not explicitly write a loop, it is hardly clearer than simply coding the loop to do what you need it to do.

Answer 2

我想这会做你想要的

cars.Select(c=>c.ResaleValue = c.Calculate());

Answer 3

You can't modify the IEnumerable<T> without projecting into a new IEnumerable with those values set to the ResaleValue property and copying over the existing properties. Ideally you would do this when you first get your IEnumerable<Car> .

IEnumerable<Car> cars = // however you set cars originally
cars = cars.Select(c => new Car
            {
                Prop1 = c.Prop1,
                Prop2 = c.Prop2,
                ResaleValue = ResaleCalculator(params)
             });

Clearly this is not ideal. On the other hand, you could ToList() your collection and use the ForEach method or a regular foreach loop:

var list = cars.ToList()
               .ForEach(c => c.ResaleValue = ResaleCalculator(c.SomeNeededParam));