Есть следующая программа.

using System;

namespace ConsoleApplication1
{
    
    class GenericException : Exception
    {
    }
    class ChildExceptionA : GenericException
    {
    }
    class ChildExceptionB : GenericException
    {
    }
    
    class Class1
    {
        [STAThread]
        static void Main(string[] args)
        {
            try
            {
                try
                {
                    Console.WriteLine("Before B thrown");
                    throw new ChildExceptionB();
                }
                catch(ChildExceptionB)
                {
                    Console.WriteLine("Got B exception !");
                    Console.WriteLine("Catch block throws A!");
                    throw new ChildExceptionA();
                }
                finally
                {
                    Console.WriteLine("Finally block throws B!");
                    throw new ChildExceptionB();
                }
            }
            catch(GenericException gex)
            {
                Console.WriteLine("Caught " + gex.GetType().ToString());
                Console.ReadLine();
            }
        }
    }
}

Есть ее вывод :

Before B thrown
Got B exception !
Catch block throws A!
Finally block throws B!
Caught ConsoleApplication1.ChildExceptionB

Внимание вопрос! Куда делся ChildExceptionA ?