重写 IComparer 以使用 lambda 表达式

Question

我正在尝试重写我IComparer<Animal>的代码以使用 lambda 表达式，但我似乎无法正确完成此操作

public class AnimalCarriageSorter : IComparer<Animal>

{

    public int Compare(Animal animal, Animal targetAnimal)

    {

        //Compare diet first.

        if (animal.FoodDiet.CompareTo(targetAnimal.FoodDiet) != 0) 

        {

            return animal.FoodDiet.CompareTo(targetAnimal.FoodDiet);

        }

        //Compare size.

        return targetAnimal.Size.CompareTo(animal.Size);

    }

}

Answer 1

您可以使用Func<Animal, Animal, int>而不是轻松地重写它IComparer<Animal>，例如Func<Animal, Animal, int> comparer = (x, y) =>&nbsp;&nbsp; &nbsp; x.FoodDiet.CompareTo(y.FoodDiet) != 0 ?&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; x.FoodDiet.CompareTo(y.FoodDiet) :&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; x.Size.CompareTo(y.Size)

Answer 2

问题是您已将比较从 切换animal.CompareTo(targetAnimal)为targetAnimal.CompareTo(animal)，因此您不会获得一致的结果。在这两种情况下，您都应该将其animal作为第一个对象。例如：public int Compare(Animal animal, Animal targetAnimal){&nbsp; &nbsp; // Compare diet first.&nbsp; &nbsp; if (animal.FoodDiet.CompareTo(targetAnimal.FoodDiet) != 0)&nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; return animal.FoodDiet.CompareTo(targetAnimal.FoodDiet);&nbsp; &nbsp; }&nbsp; &nbsp; // Compare size.&nbsp; &nbsp; return animal.Size.CompareTo(targetAnimal.Size);}或者你可以稍微简化一下：public int Compare(Animal animal, Animal targetAnimal){&nbsp; &nbsp; return animal.FoodDiet.CompareTo(targetAnimal.FoodDiet) != 0&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; ? animal.FoodDiet.CompareTo(targetAnimal.FoodDiet)&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; : animal.Size.CompareTo(targetAnimal.Size);}