C#中的运算符重载

Question

class Point
{
    private int m_PointX;
    private int m_PointY;

    public Point(int x, int y)
    {
        m_PointX = x;
        m_PointY = y;
    }

    public static Point operator+(Point point1, Point point2)
    {
        Point P = new Point();
        P.X = point1.X + point2.X;
        P.Y = point1.Y + point2.Y;

        return P;
    }
}

Example:

Point P1 = new Point(10,20);
Point P2 = new Point(30,40)
P1+P2; // operator overloading

1. Is it necessary to always declare the operator overloading function as static? What is the reason behind this?
2. If I want to overload + to accept the expression like 2+P2, how to do this?

Answer 1

1. Yes. Because you aren't dealing with instances always with the operators.
2. Just change the types to what you want.

Here is an example for #2

public static Point operator+(int value, Point point2)
{
 // logic here.
}

You will have to do the other way with the parameters if you want P2 + 2 to work.

See http://msdn.microsoft.com/en-us/library/8edha89s.aspx for more information.

Answer 2

To answer your questions:

1. Yes, you need to define them as static. They're not instance methods, they can operate on null s as well.
2. You'll have to define an operator overload where one of the parameters are of type int

Answer 3

Both of the previous answers talk about your questions, so I'm not going to intrude on those, but here is an example of using 2+P:

   public static Point operator+(int yourInt, Point point)
    {
        Point P = new Point();
        P.X = point.X + yourInt;
        P.Y = point.Y + yourInt;

        return P;
    }