MS Override Equals()准则不符合自己的标准.使用最佳实践

我正在查看Microsoft发布的重写Equals运算符的指导方针。https://msdn.microsoft.com/en-us/library/ms173147（v=vs.90）.aspx

他们声明：

Equals的新实施应遵循等于：

• x.Equals（x）返回true
• x.Equals（y）返回的值与y.Equal（x）相同
• 如果（x.Equals（y）&amp；y.Equals（z））返回true，然后x.Equals）返回true
• 只要x和y引用的对象没有被修改，x.Equals（y）的连续调用就会返回相同的值
• x.Equals（null）返回false（仅适用于不可为null的值类型。）

接下来，他们给出了基类和子类（TwoDPoint和ThreeDPoint，下面的代码）的示例，它们实现了覆盖此方法的最佳实践。

但是，这两个示例类不能满足刚刚给出的"等于的保证"。IE，TwoDPoint.Equals（ThreeDPoint）可以返回true，但ThreeDPoint.Equals将始终返回false。这使上面的第二个要点失败。

    static void Main(string[] args)
    {
        TwoDPoint twoDPoint = new TwoDPoint(1, 2);
        ThreeDPoint threeDPoint = new ThreeDPoint(1, 2, 3);
        //this will assert because twoDPoint.Equals(threeDPoint) == true 
        //but, threeDPoint.Equals(twoDPoint) == false
        AssertMicrosoftEqualsGuidelines(twoDPoint, threeDPoint, null);
    }
    /// <summary>
    /// Will Assert() if any of microsofts rules for Equals overriding fail.
    /// NOTE, x and y can not be null.
    /// https://msdn.microsoft.com/en-us/library/ms173147(v=vs.90).aspx
    /// </summary>
    static void AssertMicrosoftEqualsGuidelines(object x, object y, object z)
    {
        System.Diagnostics.Debug.Assert(x.Equals(x), "FAILED x.Equals(x) returns true.");
        System.Diagnostics.Debug.Assert(x.Equals(y) == y.Equals(x), "FAILED x.Equals(y) returns the same value as y.Equals(x).");
        if(x.Equals(y) && y.Equals(z))
        {
            System.Diagnostics.Debug.Assert(x.Equals(z), "FAILED Successive invocations of x. Equals (y) return the same value as long as the objects referenced by x and y are not modified.");
        }
        System.Diagnostics.Debug.Assert(x.Equals(y) == x.Equals(y) == x.Equals(y) == x.Equals(y), "Successive invocations of x. Equals (y) return the same value as long as the objects referenced by x and y are not modified.");
        System.Diagnostics.Debug.Assert(x.Equals(null) == false, "x.Equals (null) returns false");
    }
}
class TwoDPoint : System.Object
{
    public readonly int x, y;
    public TwoDPoint(int x, int y)  //constructor
    {
        this.x = x;
        this.y = y;
    }
    public override bool Equals(System.Object obj)
    {
        // If parameter is null return false.
        if (obj == null)
        {
            return false;
        }
        // If parameter cannot be cast to Point return false.
        TwoDPoint p = obj as TwoDPoint;
        if ((System.Object)p == null)
        {
            return false;
        }
        // Return true if the fields match:
        return (x == p.x) && (y == p.y);
    }
    public bool Equals(TwoDPoint p)
    {
        // If parameter is null return false:
        if ((object)p == null)
        {
            return false;
        }
        // Return true if the fields match:
        return (x == p.x) && (y == p.y);
    }
    public override int GetHashCode()
    {
        return x ^ y;
    }
}
class ThreeDPoint : TwoDPoint
{
    public readonly int z;
    public ThreeDPoint(int x, int y, int z)
        : base(x, y)
    {
        this.z = z;
    }
    public override bool Equals(System.Object obj)
    {
        // If parameter cannot be cast to ThreeDPoint return false:
        ThreeDPoint p = obj as ThreeDPoint;
        if ((object)p == null)
        {
            return false;
        }
        // Return true if the fields match:
        return base.Equals(obj) && z == p.z;
    }
    public bool Equals(ThreeDPoint p)
    {
        // Return true if the fields match:
        return base.Equals((TwoDPoint)p) && z == p.z;
    }
    public override int GetHashCode()
    {
        return base.GetHashCode() ^ z;
    }
}

那么，"平等保障"的指导方针是错误的吗？重写equals的人是否也应该检查这两个对象的类型是否相同？IE

if(GetType() != obj.GetType()){return false;} //include in Equals()?

真的，我想归根结底，如果所有基类字段都匹配，那么让基类equals（）方法为子类返回true是否被认为是"可以的"？从基类的角度来看，这是有道理的，但是，您最终会破坏上面的规则#2。打破这一规则会对字典和哈希集等项目产生什么影响？你会只是在问一些微妙的错误吗？