Abstract Class With Abstract Method in Console Programming in C#

using System.IO;
using System;
abstract class Shape {
    public double dim1, dim2;
    public Shape(double dimension1, double dimension2) {
        dim1 = dimension1;
        dim2 = dimension2;
    }
    abstract public double area();
}
class Rectangle: Shape {
    public Rectangle(double dimension1, double dimension2): base(dimension1, dimension2) {}
    override public double area() {
        Console.WriteLine("\nInside Area for Rectangle : ");
        return dim1 * dim2;
    }
}
class Triangle: Shape {
    public Triangle(double dimension1, double dimension2): base(dimension1, dimension2) {}
    override public double area() {
        Console.WriteLine("\nInside Area for Triangle : ");
        return dim1 * dim2 / 2;
    }
}
class AbstractClass {
    public static void Main(string[] args) {
        Rectangle newRectangle = new Rectangle(6, 7);
        Triangle newTriangle = new Triangle(12, 23);
        Shape referenceShape;
        referenceShape = newRectangle;
        Console.WriteLine("Area is " + referenceShape.area());
        referenceShape = newTriangle;
        Console.WriteLine("Area is " + referenceShape.area());
    }
}

Output:

Inside Area for Rectangle : Area is 42
Inside Area for Triangle : Area is 138