C#中的弱引用

用代码说明：

 

代码

     class  Program
    {
         static   void  Main( string [] args)
        {
            DoWork();
            Console.WriteLine(P.Target  ==   null );
            GC.Collect();
            Console.WriteLine(P.Target  ==   null );

            Console.ReadLine();
        }

         public   static  WeakReference P;
         public   static   void  DoWork()
        {
            var p  =  GetPerson();
            P  =   new  WeakReference(p);
        }

         public   static  Person GetPerson()
        {
             return   new  Person();
        }
    }
     public   class  Person : IDisposable
    {
     
         public  Person()
        {
        
             for  ( int  i  =   0 ; i  <   new  Random().Next( 18 ,  80 ); i ++ )
            {
                 this .Memo.Append(( char ) new  Random().Next( 97 ,  123 ));
            }
        }


         public  StringBuilder Memo {  get ;  set ; }


         public   bool  IsDisposed {  get ;  set ; }
         #region  IDisposable 成员

         public   void  Dispose()
        {
             if  ( ! this .IsDisposed)
            {
                Console.WriteLine( " Person Dispose... " );

                 this .Memo.Remove( 0 ,  this .Memo.Length);
                 this .IsDisposed  =   true ;
                GC.SuppressFinalize( this );
            }
        }

         #endregion

         ~ Person()
        {
            Console.WriteLine( " Person Unctor... " );
             this .Dispose();
        }
    }