question on delegate predicates

in the following class:

class testLinq

    {

       

        public  bool www(string s)

        { return s.Equals("def"); }

        public delegate bool d(string s);

        public void write()

        {

           

            List<String> l = new List<string>() { "abc", "def" };

             

            normal way of doing predicate:  

            Console.WriteLine(l.Find(p => { return p.Equals("def"); }));

            

            bizzare method: 

            Predicate<string> pred = new Predicate<string>(www); 

            Console.WriteLine(l.Find(pred));

            non working method - 

            d di = null;

            di  = www;

            Console.WriteLine(l.Find(di)));

         Why?

            

            Console.ReadLine();

        }

    }