using System.Collections.Generic;
public static void Main()
B b= new B(string.Empty,0);
Console.WriteLine(b.x + ":" + b.y);
List<B> bs = new List<B>();
bs.ForEach(item=>{item.y=-2; item.x="blah";});
Console.WriteLine(((B)bs[0]).x + ":" + ((B)bs[0]).y));
Console.WriteLine(b.x + ":" + b.y);
private static void changeB(B b)
public string x {get; set;}
public B(string x, int y)