3.1.4、结论：对于简单常见值类型 int、float、double、decimal等，Equal函数 and 运算符'=='，如果其值相等，返回true；否则，返回false。

3.2、 结构体struct

3.2.1、 ValueType内部的Equals函数

        ValueType
        {
            [System.Security.SecuritySafeCritical]
            public override bool Equals (Object obj) {
                BCLDebug.Perf(false, "ValueType::Equals is not fast.  "+this.GetType().FullName+" should override Equals(Object)");
                if (null==obj) {
                    return false;
                }
                RuntimeType thisType = (RuntimeType)this.GetType();
                RuntimeType thatType = (RuntimeType)obj.GetType();
     
                if (thatType!=thisType) {
                    return false;
                }
     
                Object thisObj = (Object)this;
                Object thisResult, thatResult;
     
                // if there are no GC references in this object we can avoid reflection 
                // and do a fast memcmp
                if (CanCompareBits(this))
                    return FastEqualsCheck(thisObj, obj);
     
                FieldInfo[] thisFields = thisType.GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
     
                for (int i=0; i<thisFields.Length; i++) {
                    thisResult = ((RtFieldInfo)thisFields[i]).UnsafeGetValue(thisObj);
                    thatResult = ((RtFieldInfo)thisFields[i]).UnsafeGetValue(obj);
                    
                    if (thisResult == null) {
                        if (thatResult != null)
                            return false;
                    }
                    else
                    if (!thisResult.Equals(thatResult)) {
                        return false;
                    }
                }
     
                return true;
            }
     
            [System.Security.SecuritySafeCritical]  // auto-generated
            [ResourceExposure(ResourceScope.None)]
            [MethodImplAttribute(MethodImplOptions.InternalCall)]
            private static extern bool CanCompareBits(Object obj);
     
            [System.Security.SecuritySafeCritical]  // auto-generated
            [ResourceExposure(ResourceScope.None)]
            [MethodImplAttribute(MethodImplOptions.InternalCall)]
            private static extern bool FastEqualsCheck(Object a, Object b);         
        }

3.2.2、结构体(只有值类型，重写Equal函数 and 运算符'==')

3.2.2.1、测试代码：

    struct Point
    {
        public double x;
        public double y;
        public double z;

        public Point(double X, double Y, double Z)
        {
            this.x = X;
            this.y = Y;
            this.z = Z;
        }

        public override bool Equals(Object obj)
        {
            if (!(obj is Point))
            {
                return false;
            }

            if (((Point)obj).x == this.x)
            {
                return true;
            }

            return false;
        }
        public bool Equals(Point obj)
        {
            if (obj.x == this.x)
            {
                return true;
            }

            return false;
        }
        
        //运算符“Point.operator ==(Point, Point)”要求也要定义匹配的运算符“!=”
        public static bool operator ==(Point left, Point right)
        {
            return left.x == right.x;
        }

        public static bool operator !=(Point left, Point right)
        {
            return left.x != right.x;
        }
    }

    Point p1 = new Point(1, 2, 3);
    Point p2 = p1;
    
    p1.y = 100;
    Console.WriteLine(p1 == p2);//返回true
    Console.WriteLine(p1.Equals(p2)); // 返回true
    Console.WriteLine(p1.Equals((object)p2)); // 返回true

3.2.2.2、结论：此时程序执行我们重写的Equal函数 and 运算符'=='。

3.2.3、结构体(只有值类型，不重写Equal函数 and 运算符'==')

3.2.3.1、测试代码：

    struct Point
    {
        public double x;
        public double y;
        public double z;

        public Point(double X, double Y, double Z)
        {
            this.x = X;
            this.y = Y;
            this.z = Z;
        }
    }

    Point p1 = new Point(1, 2, 3);
    Point p2 = p1;

    Console.WriteLine(p1 == p2);//编译错误：运算符"=="无法应用于"Point"和"Point"类型的操作数
    Console.WriteLine(p1.Equals(p2)); // 返回true
    Console.WriteLine(p1.Equals((object)p2)); // 返回true
    p1.y = 100;
    Console.WriteLine(p1.Equals(p2)); // 返回false
    Console.WriteLine(p1.Equals((object)p2)); // 返回false