liskov.cs

using System;
/// <summary>
/// Introduces new class <c>Shape</c>
/// </summary>
class Shape
{
    /// <summary>
    /// Initializes public method <c>Area</c>
    /// </summary>
    /// <returns>Returns area, throws exception with custom message</returns>
    public virtual int Area()
    {
        throw new NotImplementedException("Area() is not implemented");
    }
}

/// <summary>
/// New class <c>Rectangle</c> inheriting from <c>Shape</c>
/// </summary>
class Rectangle : Shape
{
    private int width;
    private int height;

    public int Width
    {
        get { return width; }
        set
        {
            if (value < 0) { throw new ArgumentException("Width must be greater than or equal to 0"); }
            width = value;
        }
    }

    public int Height
    {
        get { return height; }
        set
        {
            if (value < 0) { throw new ArgumentException("Height must be greater than or equal to 0"); }
            height = value;
        }
    }

    /// <summary>
    /// override of <c>Area()</c> method defined in base class
    /// </summary>
    /// <returns>Returns area of shape</returns>
    public new int Area()
    {
        return height * width;
    }

    /// <summary>
    /// returns string output with rectangle dimensions
    /// </summary>
    public override string ToString()
    {
        return ($"[Rectangle] {width} / {height}");
    }
}

class Square : Rectangle
{
    private int size;

    public int Size
    {
        get { return size; }
        set
        {
            if (size < 0) { throw new ArgumentException("Size must be greater than or equal to 0"); }
            size = Height = Width = value;
        }
    }

    /// <summary>
    /// returns string output with square dimensions
    /// </summary>
    public override string ToString()
    {
        return ($"[Square] {size} / {size}");
    }
}

class Program
{
 static void Main(string[] args)
 {
 Square aSquare = new Square();
try
 {
 aSquare.Width = 12;
 aSquare.Height = 8;
Console.WriteLine("aSquare width: {0}", aSquare.Width);
 Console.WriteLine("aSquare height: {0}", aSquare.Height);
 Console.WriteLine("aSquare size: {0}", aSquare.Size);
 Console.WriteLine("aSquare area: {0}", aSquare.Area());
 Console.WriteLine(aSquare.ToString());
 }
 catch (Exception e)
 { 
 Console.WriteLine(e);
 }
 }
}
// Output:
//
// aSquare width: 12
// aSquare height: 8
// aSquare size: 0
// aSquare area: 96
// [Square] 0 / 0