csharp

public class A { protected int i; public A (int i) { this.i = i; } }

public class B : A { public B (int i) : base (i + 1) { } public bool Foo (Object myObject) { Console.WriteLine ("Foo1"); return ((myObject is B) && (this.i == ((B)myObject).i)); } public virtual bool Foo (B myB, int num) { Console.WriteLine ("Foo2"); return (this.i + myB.i) < num; } }

public class C : B { public C (int i) : base (i) { } public bool Foo (int num) { Console.WriteLine ("Foo3"); return (this.i != num); } }

public class D : B { public D (int i) : base (i * 2) { } public override bool Foo (B myB, int num) { Console.WriteLine ("Foo4"); return base.Foo (myB, 20 ); } }

// --- המחלקה Tester (סעיף ב) --- public class Tester { public static void Main (string[] args) { A a = new A (1); B b = new B (2); C c = new C (3); D d = new D (4); B bd = new D (5); A ac = new C (6); //*** } }