using System;

class Program
    {
        public static void Main()
        {
            try
            {
                using (D d = new D())
                {
                    Console.WriteLine("using D");
                }
            }
            catch (Exception ) { Console.WriteLine("catch"); }

            Console.ReadKey();
        }
    }
    class D : IDisposable
    {
        IDisposable a = null;
        IDisposable b = null;
        public void Dispose()
        {
            try { a.Dispose(); }
            finally
            {
                try { b.Dispose(); }
                finally
                {
                }
            }
        }
    }