c# - Compare() 方法，Parent 和 Children 对象排序不完美

Question

我有这个作业。而我初学C#程序，现在学习C#和Java

作业: 编写获取 Drink[] 数组的静态方法，其中 AlcoholDrink 具有不同的酒精值。该方法返回一个包含三个最高酒精值的数组!如果数组中没有那么多 AlcoholDrink，则该方法返回空引用!

我试过写这个方法，但它不能正常工作......

因为 sz[1] = (AlcoholDrink)t[1]; 它是一个 Drink 对象(非酒精)，我不明白为什么它在那里...

或者我的Compare方法不完美，可能有错误...我怎样才能瞄准，非AlcoholDrink对象(Drink Objects)到数组的末尾？

这是我的 C# 代码:

    class DrinkComparer : IComparer<Drink>
    {
        public int Compare(Drink x, Drink y)
        {
            // AlcoholDrink class is children of Drink class
            if (x is AlcoholDrink && y is AlcoholDrink)
            {
                AlcoholDrink a = (AlcoholDrink)x;
                AlcoholDrink b = (AlcoholDrink)y;
                double aAlk = a.GetValueOfAlcohol; 
                double bAlk = b.GetValueOfAlcohol;
                if (aAlk > bAlk)
                    return -1;
                else if (aAlk < bAlk)
                    return 1;
                else
                    return 0;
            }
            // Drink objects haven't got GetValueOfAlcohol method...
            // How can I aim, the non AlcoholDrink objects (Drink objects) go to the end     array?
            else
                return 1;                
        }
    }
    static AlcoholDrink[] Largest3AlcoholDrink(Drink[] t)
    {
        Array.Sort(t, new DrinkComparer());
        AlcoholDrink[] sz = new AlcoholDrink[3];
        sz[0] = (AlcoholDrink)t[0];
        sz[1] = (AlcoholDrink)t[1];
        sz[2] = (AlcoholDrink)t[2];
        return sz;
    }
        AlcoholDrink sz = new AlcoholDrink( "Kékfrankos" , "0.75 l", 1500, 4.5);
        Console.WriteLine(sz);

        Drink[] t = new Drink[8];
        t[0] = new AlcoholDrink("Kék Portói", "0.75 l", 1200, 20.5);
        t[1] = new Drink("Tocsik", "0.75 l", 1100); // Non Alcohol Drink
        t[2] = new AlcoholDrink("Tokaji Asszú", "0.75 l ", 1600, 14.5);
        t[3] = new AlcoholDrink("Egri Bikavér", "0.75 l", 1500, 23.5);
        t[4] = new Drink("Egri Szamóca", "0.75 l", 1100); // Non Alchol Drink
        t[5] = new AlcoholDrink("Egri Merlot", "0.75 l", 1700, 18.5);
        t[6] = new AlcoholDrink("Egri Medina", "0.75 l", 900, 16.5);
        t[7] = new AlcoholDrink("Törley Talisman", "0.75 l", 750, 4.5);
        Console.WriteLine(DrinkKeres( t, "Egri Bikavér"));

        Largest3AlcoholDrink(t);

        Console.ReadLine();

Answer 1

问题在这里:

        // Drink objects haven't got GetValueOfAlcohol method...
        // How can I aim, the non AlcoholDrink objects (Drink objects) go to the end     array?
        else
            return 1;

您希望非酒精饮料走到最后，但即使其中一种饮料是酒精饮料，这也会返回 1。这样做:

else if (x is AlcoholicDrink) return -1;
else if (y is AlcoholicDrink) return 1;
else return 0;