Nested Class Problem in C#

Question

Hi
i have make a program in which two nested classes one is outer class and other is inner class and just i have make their just constructor and i inherit them with the main class demo when ever i make an object of demo class by default outer class constructor is calling can any one tell me why it is calling although i am not making outer class object why it is calling....................? w8ing for rep

class demo :outerClass

    {

        static void Main(string[] arg)

        {

            demo d = new demo();

        }

    }

    class outerClass

    {

        public outerClass()

        { 

               Console.WriteLine ("This is outer constructor");

        }

        class innerClass

        {

            public innerClass()

            {

                Console.WriteLine("This is inner class constructor");

            }

        }

    }