internal class Person

 {

     public string FirstName { get; set; }

     public string LastName { get; set; }

     public string FullName

     {

         get { return FirstName + LastName; }

     }

     public override string ToString()

     {

         return string.Format("[firstname={0},lastname={1}]", FirstName, LastName);

     }

 }

 internal class Person

 {

     public string FirstName { get; set; }

     public string LastName { get; set; }

     public string FullName => FirstName + LastName;

     public override string ToString() => string.Format("[firstname={0},lastname={1}]", FirstName, LastName);

 }

 internal class Point

 {

     public int X { get; private set; }

     public int Y { get; private set; }

     public Point(int x, int y)

     {

         this.X = x;

         this.Y = y;

     }

     public Point Add(Point other)

     {

         return new Point(this.X + other.X, this.Y + other.Y);

     }

     //方法1，有返回值

     public Point Move(int dx, int dy) => new Point(X + dx, Y + dy);

     //方法2，无返回值

     public void Print() => Console.WriteLine(X + "," + Y);

     //静态方法，操作符重载

     public static Point operator +(Point a, Point b) => a.Add(b);

     //只读属性，只能用于只读属性

     public string Display => "[" + X + "," + Y + "]";

     //索引器

     public int this[long id] => ;

 }

 internal class Program

 {

     private static void Main()

     {

         Point p1 = new Point(, );

         Point p2 = new Point(, );

         Point p3 = p1 + p2;

         //输出:[3,4]

         Console.WriteLine(p3.Display);

     }

 }