using System; class A { public void F() { Console.WriteLine("A.F"); } public virtual void G() { Console.WriteLine("A.G"); } } class B: A { new public void F() { Console.WriteLine("B.F"); } public override void G() { Console.WriteLine("B.G"); } } class Test { static void Main() { B b = new B(); A a = b; a.F(); b.F(); a.G(); b.G(); } }In the example, A introduces a non-virtual method F and a virtual method G. The class B introduces a new non-virtual method F, thus hiding the inherited F, and also overrides the inherited method G. The example produces the output:
A.F B.F B.G B.GNotice that the statement a.G() invokes B.G, not A.G. This is because the run-time type of the instance (which is B), not the compile-time type of the instance (which is A), determines the actual method implementation to invoke. end example] Paragraph 51 Because methods are allowed to hide inherited methods, it is possible for a class to contain several virtual methods with the same signature. 2 This does not present an ambiguity problem, since all but the most derived method are hidden. [Example: In the example
using System; class A { public virtual void F() { Console.WriteLine("A.F"); } } class B: A { public override void F() { Console.WriteLine("B.F"); } } class C: B { new public virtual void F() { Console.WriteLine("C.F"); } } class D: C { public override void F() { Console.WriteLine("D.F"); } } class Test { static void Main() { D d = new D(); A a = d; B b = d; C c = d; a.F(); b.F(); c.F(); d.F(); } }the C and D classes contain two virtual methods with the same signature: The one introduced by A and the one introduced by C. The method introduced by C hides the method inherited from A. Thus, the override declaration in D overrides the method introduced by C, and it is not possible for D to override the method introduced by A. The example produces the output:
B.F B.F D.F D.FNote that it is possible to invoke the hidden virtual method by accessing an instance of D through a less derived type in which the method is not hidden. end example]
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