不要在构造中做太多事情，不然有时候会出现有意思的代码~

一段有意思的代码：

namespace TestHahaha
{
    class Program
    {
       
        static void Main(string[] args)
        {
            A a = new A();
            a.Print();
        }

    }

    public class A
    {
        public B bObj = null;

        public A()
        {
            bObj = new B(this);
        }

        public void Print()
        {
            if (bObj == null)
                Console.Write("bObj == null");
            else
                Console.Write("bObj != null");
        }

        public void SetBNull()
        {
            bObj = null;
        }
    }

    public class B
    {
        public A aObj = null;

        public B(A a)
        {
            aObj = a;
            a.SetBNull();
        }
    }
}

答案是：bObj != null;