refactor: 擷取IShape介面。

AreaOfShapeCalulations/Calculator.cs

@@ -2,14 +2,9 @@
 {
     public class Calculator
     {
-        public double GetTotalArea(Rectangle rectangle)
+        public double GetTotalArea(IShape shape)
         {
-            return rectangle.Area();
-        }
-
-        public double GetTotalArea(Square square)
-        {
-            return square.Area();
+            return shape.Area();
         }
     }
 }

AreaOfShapeCalulations/IShape.cs

@@ -0,0 +1,7 @@
+namespace AreaOfShapeCalulations
+{
+    public interface IShape
+    {
+        double Area();
+    }
+}

AreaOfShapeCalulations/Rectangle.cs

@@ -1,6 +1,6 @@
 namespace AreaOfShapeCalulations
 {
-    public class Rectangle
+    public class Rectangle : IShape
     {
         private readonly double _height;
         private readonly double _width;
@@ -11,7 +11,7 @@ public Rectangle(double height, double width)
             _width = width;
         }
 
-        internal double Area()
+        public double Area()
         {
             return _height * _width;
         }

AreaOfShapeCalulations/Square.cs

@@ -1,6 +1,6 @@
 namespace AreaOfShapeCalulations
 {
-    public class Square
+    public class Square : IShape
     {
         private readonly double _length;
 
@@ -9,7 +9,7 @@ public Square(double length)
             _length = length;
         }
 
-        internal double Area()
+        public double Area()
         {
             return _length * _length;
         }