111

cs5/5_4/5_4.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <RootNamespace>_5_4</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

cs5/5_4/5_4.sln

@@ -0,0 +1,25 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.14.36616.10 d17.14
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "5_4", "5_4.csproj", "{43F29EB3-99B5-4064-911E-3B3570272923}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{43F29EB3-99B5-4064-911E-3B3570272923}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{43F29EB3-99B5-4064-911E-3B3570272923}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{43F29EB3-99B5-4064-911E-3B3570272923}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{43F29EB3-99B5-4064-911E-3B3570272923}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {20D2A0A1-A7D4-4CAC-BC03-AACF2D5F63B0}
+	EndGlobalSection
+EndGlobal

cs5/5_4/Program.cs

@@ -0,0 +1,60 @@
+namespace _5_4
+{
+    public abstract class Shape
+    {
+        protected string name;
+        public Shape(string name)
+        {
+            this.name = name;
+        }
+        public abstract void Show();
+        public abstract double Area();
+    }
+    public class Rectangle : Shape
+    {
+        protected double width;
+        protected double height;
+        public Rectangle(string name, double width, double height) : base(name)
+        {
+            this.width = width;
+            this.height = height;
+        }
+        public override void Show()
+        {
+            Console.WriteLine("Rectangle: {0} , area :{1}", name, width * height);
+        }
+        public override double Area()
+        {
+            return width * height;
+        }
+    }
+    public class Circle : Shape
+    {
+        protected double radius;
+        public Circle(string name, double radius) : base(name)
+        {
+            this.radius = radius;
+        }
+        public override void Show()
+        {
+            Console.WriteLine("Circle: {0} , area :{1}", name, Math.PI * radius * radius);
+        }
+        public override double Area()
+        {
+            return Math.PI * radius * radius;
+        }
+    }
+    public class Program
+    {
+        static void Main(string[] args)
+        {
+            Shape[] s = { new Rectangle("小矩形",1.0,2.0),
+                         new Circle("大源",5.0),
+                        };
+            foreach (Shape shape in s)
+            {
+                shape.Show();
+            }
+        }
+    }
+}