Setting behaviour dynamically

Ch1Duck/Duck.cs

@@ -1,14 +1,16 @@
 namespace Ch1Duck;
 
 public abstract class Duck(IFlyBehaviour flyBehaviour, IQuackBehaviour quackBehaviour) {
+    internal IFlyBehaviour FlyBehaviour { get; set; } = flyBehaviour;
+    internal IQuackBehaviour QuackBehaviour { get; set; } = quackBehaviour;
     public abstract void Display();
 
     public void PerformFly() {
-        flyBehaviour.Fly();
+        FlyBehaviour.Fly();
     }
     
     public void PerformQuack() {
-        quackBehaviour.Quack();
+        QuackBehaviour.Quack();
     }
 }
 
@@ -16,4 +18,10 @@ public class MallardDuck() : Duck(new FlyWithWings(), new NormalQuack()) {
     public override void Display() {
         Console.WriteLine("I'm a real Mallard duck");
     }
+}
+
+public class ModelDuck() : Duck(new FlyNoWay(), new NormalQuack()) {
+    public override void Display() {
+        Console.WriteLine("I'm a model duck");
+    }
 }

Ch1Duck/Fly.cs

@@ -14,4 +14,10 @@ public class FlyNoWay: IFlyBehaviour {
     public void Fly() {
         Console.WriteLine("I can't fly");
     }
+}
+
+public class FlyRocketPowered: IFlyBehaviour {
+    public void Fly() {
+        Console.WriteLine("I'm flying with a rocket!");
+    }
 }

Ch1Duck/Program.cs

@@ -4,4 +4,9 @@ using Ch1Duck;
 
 Duck mallard = new MallardDuck();
 mallard.PerformQuack();
-mallard.PerformFly();
+mallard.PerformFly();
+
+Duck model = new ModelDuck();
+model.PerformFly();
+model.FlyBehaviour = new FlyRocketPowered();
+model.PerformFly();