Ch3Beverage: My version of a Decorator without the construction and hold of the Beverage inside the decorator abstract class.

Ch3Beverage/Beverage.cs

@@ -0,0 +1,51 @@
+namespace Ch3Beverage;
+
+public abstract class Beverage {
+    public virtual string Description => "Unknown beverage";
+
+    public abstract double Cost();
+}
+
+/*
+   The only real benefit of putting the constructor in CondimentDecorator is if you need to:
+   Add validation logic (e.g., null checks) once for all decorators
+   Add shared behavior that all decorators need when wrapping
+   Enforce that the wrapped beverage is immutable across all decorators
+ *
+   If you don't need shared initialization logic, your approach is cleaner and more direct.
+   It's a legitimate design choice, not a mistake.
+   The "always put it in the base class" advice is dogmatic - useful when you have multiple decorators and want consistency,
+   but not a hard rule. Your implementation follows the Decorator pattern correctly.
+ */
+
+public abstract class CondimentDecorator : Beverage;
+
+public class Espresso : Beverage {
+    public override string Description => "Espresso";
+
+    public override double Cost() => 1.99;
+}
+
+public class HouseBlend : Beverage {
+    public override string Description => "House Blend Coffee";
+
+    public override double Cost() => 0.89;
+}
+
+public class DarkRoast : Beverage {
+    public override string Description => "Dark Roast Coffee";
+
+    public override double Cost() => 0.99;
+}
+
+public class Decaf : Beverage {
+    public override string Description => "Decaf Coffee";
+
+    public override double Cost() => 1.05;
+}
+
+public class Mocha(Beverage beverage) : CondimentDecorator {
+    public override string Description => $"{beverage.Description}, Mocha";
+
+    public override double Cost() => beverage.Cost() + 0.20;
+}

Ch3Beverage/Ch3Beverage.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <OutputType>Exe</OutputType>
+        <TargetFramework>net9.0</TargetFramework>
+        <LangVersion>latestmajor</LangVersion>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+    </PropertyGroup>
+
+</Project>

Ch3Beverage/Program.cs

@@ -0,0 +1,3 @@
+// See https://aka.ms/new-console-template for more information
+
+Console.WriteLine("Hello, World!");

HeadFirstDesignPatterns.sln

@@ -4,6 +4,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Ch1Duck", "Ch1Duck\Ch1Duck.
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Ch2Weather", "Ch2Weather\Ch2Weather.csproj", "{D457D364-C0AB-42D2-A0B7-245D038CE8D1}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Ch3Beverage", "Ch3Beverage\Ch3Beverage.csproj", "{8F380143-DDBC-4785-B4F2-7B32EBE54515}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -18,5 +20,9 @@ Global
 		{D457D364-C0AB-42D2-A0B7-245D038CE8D1}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{D457D364-C0AB-42D2-A0B7-245D038CE8D1}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{D457D364-C0AB-42D2-A0B7-245D038CE8D1}.Release|Any CPU.Build.0 = Release|Any CPU
+		{8F380143-DDBC-4785-B4F2-7B32EBE54515}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{8F380143-DDBC-4785-B4F2-7B32EBE54515}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{8F380143-DDBC-4785-B4F2-7B32EBE54515}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{8F380143-DDBC-4785-B4F2-7B32EBE54515}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 EndGlobal