1.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            person p1 = new person();
            p1.Name 
 
= "ZhangTao";
 
            WeakReference wkr = new WeakReference(p1);
            p1 = null;  
            GC.Collect(); // 強制進行垃圾回收
            
            //object wP1 = wkr.Target;
            //if (wP1 != null)
            //{
            //    Console.WriteLine(((person)wP1).Name);
            
 
//}
            //else
            //{
            //    Console.WriteLine("對象已被回收");
            //}
            ThreadPool.QueueUserWorkItem(h =>
            {
                object wP1 = wkr.Target;
                if (wP1 != null)
                {
                    Console.WriteLine(((person)wP1).Name);
                }
                
 
else
                {
                    Console.WriteLine("對象已被回收");
                }
            });
            Console.ReadKey();
        }
    }
   
    class person
    {
        public string Name { get; set; }
    }
}

C#系統之垃圾回收