Fix Liskov Subsutution bad example

README.md

@@ -2037,58 +2037,63 @@ get into trouble.
 **Bad:**
 
 ```csharp
+using System;
+using System.Collections.Generic;
+
 class Rectangle
 {
- protected double Width = 0;
- protected double Height = 0;
-
- public Drawable Render(double area)
- {
- // ...
- }
-
- public void SetWidth(double width)
- {
- Width = width;
- }
+ protected double Width = 0;
+ protected double Height = 0;
+
+ public void SetWidth(double width)
+ {
+ Width = width;
+ }
 
- public void SetHeight(double height)
- {
- Height = height;
- }
+ public void SetHeight(double height)
+ {
+ Height = height;
+ }
 
- public double GetArea()
- {
- return Width * Height;
- }
+ public double GetArea()
+ {
+ return Width * Height;
+ }
 }
 
 class Square : Rectangle
 {
- public double SetWidth(double width)
- {
- Width = Height = width;
- }
-
- public double SetHeight(double height)
- {
- Width = Height = height;
- }
+ public void SetLength(double length)
+ {
+ Width = length;
+ Height = length;
+ }
+}
+
+public class Program
+{
+ public static void Main()
+ {
+ IList<Rectangle> list = new List<Rectangle>()
+ {new Square(), new Rectangle(), new Rectangle()};
+ foreach (Rectangle rectangle in list)
+ {
+ if (rectangle is Rectangle)
+ {
+ rectangle.SetHeight(4);
+ rectangle.SetWidth(5);
+ }
+
+ if (rectangle is Square)
+ {
+ ((Square)rectangle).SetLength(5);
+ }
+
+ double area = rectangle.GetArea();
+ Console.WriteLine(area.ToString());
+ }
+ }
 }
-
-Drawable RenderLargeRectangles(Rectangle rectangles)
-{
- foreach (rectangle in rectangles)
- {
- rectangle.SetWidth(4);
- rectangle.SetHeight(5);
- var area = rectangle.GetArea(); // BAD: Will return 25 for Square. Should be 20.
- rectangle.Render(area);
- }
-}
-
-var rectangles = new[] { new Rectangle(), new Rectangle(), new Square() };
-RenderLargeRectangles(rectangles);
 ```
 
 **Good:**