Simple demonstration of how polymorphism through method overriding and hiding works in C# (Unity compatible)

MethodOverridingDemoUnity.cs

using UnityEngine;

namespace PolymorphismDemo
{
	public class A
	{
		public virtual void Foo() { Debug.Log ("A.Foo()"); }
	}

	public class B : A
	{
		public new void Foo() { Debug.Log ("B.Foo()"); }              // Static binding (hiding)
	}

	public class C : A
	{
		public override void Foo() { Debug.Log ("C.Foo()"); }         // Dynamic binding (overriding)
	}

	/*public class D : A                                            // WARNING: new or override required
  {
    public void Foo() { Debug.Log("D.Foo()"); }
  }*/

	public class E : C
	{
		public sealed override void Foo() { Debug.Log ("E.Foo()"); }  // C.Foo() is implicitly virtual
	}

	/*public class F : E                                            // ERROR: sealed method cannot be overridden
	{
	  public override void Foo() { Debug.Log("F.Foo()"); }
	}*/

	public class G : E
	{
		public new void Foo() { Debug.Log ("G.Foo()"); }              // ... but it can be hidden
	}

	class MethodOverridingDemo
	{
		static void Test()
		{
			A thing = new A();
			B thing2 = new B();
			C thing3 = new C();

			A thing4 = thing2;
			A thing5 = thing3;

			A thing6 = new E();
			A thing7 = new G();

			thing.Foo();     // A.Foo()
			thing2.Foo();    // B.Foo()
			thing3.Foo();    // C.Foo()

			thing4.Foo();    // A.Foo()
			thing5.Foo();    // C.Foo()

			thing6.Foo();    // E.Foo()
			thing7.Foo();    // E.Foo()
		}
	}
}