程序的输出结果是： class Program { static void Main(string[] args) { Triangle t = new Triangle(3, 4); double s = t.area(); Console.WriteLine("area is {0}",s); Console.ReadLine(); } } class Shape { protected double width; protected double height; public Shape() { width = height = 0; } public Shape(double w, double h) { width = w; height = h; } public virtual double area() { return width * height; } } class Triangle : Shape { public Triangle(double x, double y) : base(x, y) { } public override double area() { return width * height / 2; } }