class CMyClassNew : public CMyClass
{
public:
	virtual void Test()
	{
		CMyClass::Test(); 
		Console::WriteLine("CMyClassNew Test"); 
	}
};

Visual Basic.Net

Class CMyClassNew
	Inherits CMyClass
	Public Overrides Sub Test()
		MyBase.Test()
		MsgBox("CMyClassNew")
	End Sub
End Class

CSharp

namespace ConsoleApplication2
{
	using System;

	class CMyClass
	{
		public virtual void Test()
		{
			Console.WriteLine("CMyClass");
		}
	}

	class CMyClassNew : CMyClass 
	{
		public virtual void Test()
		{
			base.Test(); 
			Console.WriteLine("CMyClassNew"); 
		}
	}

	public class Class1
	{
		public static int Main(string[] args)
		{
			CMyClassNew cm = new CMyClassNew();
			cm.Test(); 
			Console.Read(); 
			return 0;
		}
	}
}