使用 linq 从 IEnumerable 中排除类型
如何使用 linq-to-objects 根据对象的派生类型过滤对象？
我正在寻找性能最佳的解决方案。
使用的类：
abstract class Animal { }
class Dog : Animal { }
class Cat : Animal { }
class Duck : Animal { }
class MadDuck : Duck { }
我知道三种方法：使用 is 关键字、使用 Except 方法和使用 OfType 方法。
List<Animal> animals = new List<Animal>
{
new Cat(),
new Dog(),
new Duck(),
new MadDuck(),
};
// Get all animals except ducks (and or their derived types)
var a = animals.Where(animal => (animal is Duck == false));
var b = animals.Except((IEnumerable<Animal>)animals.OfType<Duck>());
// Other suggestions
var c = animals.Where(animal => animal.GetType() != typeof(Duck))
// Accepted solution
var d = animals.Where(animal => !(animal is Duck));
How can I filter out objects based on their derived type with linq-to-objects?
I am looking for the solution with the best performance.
The classes used:
abstract class Animal { }
class Dog : Animal { }
class Cat : Animal { }
class Duck : Animal { }
class MadDuck : Duck { }
I know of three methods: Use the is keyword, use the Except method, and to use the OfType method.
List<Animal> animals = new List<Animal>
{
new Cat(),
new Dog(),
new Duck(),
new MadDuck(),
};
// Get all animals except ducks (and or their derived types)
var a = animals.Where(animal => (animal is Duck == false));
var b = animals.Except((IEnumerable<Animal>)animals.OfType<Duck>());
// Other suggestions
var c = animals.Where(animal => animal.GetType() != typeof(Duck))
// Accepted solution
var d = animals.Where(animal => !(animal is Duck));
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评论（4）
如果您还想排除 Duck 的子类，那么
is是最好的。您可以将代码缩短为.Where(animal => !(animal is Duck));否则，sll 推荐的 GetType 是最好的
If you want to also exclude subclasses of Duck, then the
isis best. You can shorten the code to just.Where(animal => !(animal is Duck));Otherwise, sll's recommendation of GetType is best
Except()的解决方案相当繁重。请记住，解决方案
是- 即使某些从Duck继承的SomeDuck类也会返回true其他解决方案可以是：
Except()is quite heavy.Keep in mind that solution
is- would return true even someSomeDuckclass inherited fromDuckAn other solution could be:
根据 OfType<>() 和检查类型之间的差异Where() 扩展 OfType 调用等效于您的选项 (a)，尽管 is Duck==true，因此基于此我会说坚持选项 (a)。
According to Difference between OfType<>() and checking type in Where() extension the OfType call is equivalent to your option (a), albeit with is Duck==true, so based on that I would say stick to option (a).
如果您不希望返回
Duck或Duck的任何子类，则需要使用IsAssignableFrom方法：If you don't want
Ducknor any subclass ofDuckto be returned, you need to use theIsAssignableFrommethod: