38 派生类中的构造函数 object类，ToString

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication4
{
class Program
{
static void Main(string[] args)
{
B c = new B();
c.A = 700;
string d = c.ToString();
Console.WriteLine(d);
}
}
class B
{
private int a;
public int A
{
get { return a; }
set { a = value; }
}
public virtual string ToString()
{
return "我是" + a;
}
}
}