比较两个未知类型的对象以在 .NET 中进行排序

Question

我的任务：我有一个对象值数组，我需要对它们进行排序。在大多数情况下，值具有相同的原始数据类型（Int32、DateTime 或 String）；但是，在其他情况下，我们可以在此数组中包含多种类型的数据（例如整数和多个字符串）。存储在数组中的值的类型在编译时是未知的。

为了解决这个任务，我编写了一个自定义比较器，用于相应的 `Array.Sort(Array array, IComparer comparer))' 调用。比较两个对象值的方法如下所示：

public static int CompareObjects(object valueX, object valueY)
{
    IComparable myValueX = valueX as IComparable;
    IComparable myValueY = valueY as IComparable;
    if (myValueX == null)
    {
        if (myValueY == null)
            return 0;
        return -1;
    }
    if (myValueY == null)
        return 1;

    if (!Type.Equals(myValueX, myValueY))
        return string.CompareOrdinal(myValueX.GetType().Name, myValueY.GetType().Name);

    return myValueX.CompareTo(myValueY);
}

我的测试表明这种方法是一个瓶颈，我需要加快速度。有没有更快的方法来比较两个未知类型的值？

Answer 1

如果您不需要主要按类型名称排序的对象（函数成本的很大一部分），这可以修复类型比较错误，并在一个简单的测试用例中使用不同类型都实现 IComparable，还提供了 25% 的实测性能提升（在没有 Type.GetHashCode() 优化的相同功能上）：

    public static int CompareObjects(object valueX, object valueY)
    {
        IComparable myValueX = valueX as IComparable;
        IComparable myValueY = valueY as IComparable;
        if (myValueX == null)
        {
            if (myValueY == null)
                return 0;
            return -1;
        }
        if (myValueY == null)
            return 1;
        Type typeX = valueX.GetType();
        Type typeY = valueY.GetType();
        if (!typeX.Equals(typeY))
        {
            int ret = typeX.GetHashCode().CompareTo(typeY.GetHashCode());
            if (ret != 0) return ret;
            return string.CompareOrdinal(typeX.Name, typeY.Name);
        }

        return myValueX.CompareTo(myValueY);
    }

请注意，此实现也存在问题，因为它无法正确比较未从 IComparable 继承的对象。这对您来说可能是也可能不是问题。

对于持怀疑态度的人，这里有一个简单的程序，证明在 Types 上比较 GetHashCode() 是一种性能改进：

class Program
{
    class Comparable1 : IComparable<Comparable1>, IComparable
    {
        private int _value;
        public Comparable1()
        {
            _value = new Random().Next();
        }
        public int CompareTo(Comparable1 other)
        {
            return _value.CompareTo(other._value);
        }

        public int CompareTo(object obj)
        {
            return CompareTo(obj as Comparable1);
        }
    }
    class Comparable2 : IComparable<Comparable2>, IComparable
    {
        private int _value;
        public Comparable2()
        {
            _value = new Random().Next();
        }
        public int CompareTo(Comparable2 other)
        {
            return _value.CompareTo(other._value);
        }

        public int CompareTo(object obj)
        {
            return CompareTo(obj as Comparable2);
        }
    }
    static void Main(string[] args)
    {
        Comparable1 x = new Comparable1();
        Comparable2 y = new Comparable2();
        Stopwatch version1 = Stopwatch.StartNew();
        for (int round = 0; round < 10000000; ++round)
        {
            CompareObjects1(x, y);
        }
        version1.Stop();
        Stopwatch version2 = Stopwatch.StartNew();
        for (int round = 0; round < 10000000; ++round)
        {
            CompareObjects2(x, y);
        }
        version2.Stop();
        Console.WriteLine("Time1=" + version1.ElapsedTicks.ToString() + ", Time2=" + version2.ElapsedTicks.ToString());
    }
    public static int CompareObjects1(object valueX, object valueY)
    {
        IComparable myValueX = valueX as IComparable;
        IComparable myValueY = valueY as IComparable;
        if (myValueX == null)
        {
            if (myValueY == null)
                return 0;
            return -1;
        }
        if (myValueY == null)
            return 1;
        Type typeX = valueX.GetType();
        Type typeY = valueY.GetType();
        if (!typeX.Equals(typeY))
        {
            return string.CompareOrdinal(typeX.Name, typeY.Name);
        }

        return myValueX.CompareTo(myValueY);
    }
    public static int CompareObjects2(object valueX, object valueY)
    {
        IComparable myValueX = valueX as IComparable;
        IComparable myValueY = valueY as IComparable;
        if (myValueX == null)
        {
            if (myValueY == null)
                return 0;
            return -1;
        }
        if (myValueY == null)
            return 1;
        Type typeX = valueX.GetType();
        Type typeY = valueY.GetType();
        if (!typeX.Equals(typeY))
        {
            int ret = typeX.GetHashCode().CompareTo(typeY.GetHashCode());
            if (ret != 0) return ret;
            return string.CompareOrdinal(typeX.Name, typeY.Name);
        }

        return myValueX.CompareTo(myValueY);
    }
}