Merge pull request #1 from deviantdear/LiskovSubstitution

Liskov Substitution Principle Added

Author: deviantdear

scripts/InterfaceSegregationPrinciple.cs

@@ -0,0 +1,12 @@
+using System;
+
+namespace DesignPrinciples {
+
+    public class InterfaceSegregationPrinciple
+    {
+	    public InterfaceSegregationPrinciple()
+	    {
+	    }
+    }
+
+}

scripts/LiskovSubstitution.cs

@@ -0,0 +1,76 @@
+using System;
+using Systemm.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using static System.Console;
+
+namespace DesignPrinciples
+{
+    public class Rectangle
+    {
+        public virtual int Width { get; set; }
+        public virtual int Height { get; set; }
+
+        //Overloaded Constructors
+        public Rectangle()
+        {
+
+        }
+
+        publice Rectangle(int width, int height)
+        {
+            Width = width;
+            Height = height;
+        }
+
+        //Formats the return text
+        public override string ToString()
+        {
+            return $"{nameof(Width)}: {Width}, {nameof(Height)}: {Height}";
+        }
+    }
+
+    //Created below is a Square class that seems workable and will sometimes get the results you want...
+    //..but! Because the way that Square inherited from rectangle means you cannot substitute the Rectangle for the Square 
+    // without running into errors when you reset just the width or height on the rectangle
+    //You must make the properties of the Rectangle above virtual so you can override them in the square class
+    public class Square : Rectangle
+    {
+        public override int Width
+        {
+            set
+            {
+                base.Width = base.Height = value;
+            }
+        }
+        public override int Height
+        {
+            set
+            {
+                base.Width = base.Height = value;
+            }
+        }
+    }
+
+    #region Description of Principle
+    //Liskov Substitution is the "L" in the SOLID principles of OOP attributed to Barbara Liskov of MIT
+    // Object Oriented Programming Principle stating that in a computer program that 2 objects in 
+    //a subtype can be substituted without altering any type of the desirable properties of the program
+    #endregion
+
+    public class LiskovSubstitution
+    {
+         //Lambda operator returning value of the area
+
+        static public int Area(Rectangle r) => r.Width * r.Height;
+
+        public static void Main(string[] args)
+        {
+            Rectangle rc = new Rectangle();
+            WriteLine($"{rc} has area { Area(rc)}");
+        }
+    }
+}