class B
{
public int x;
public int y;
public int z;
}
class A
{
public B = new b();
}

A a = new A();
a.b.x = 1;

------解决方案--------------------
public ClassA
{
  public ClassB b{ get; set; }
}

public ClassB
{
  public string x { get; set; }  
  public string y { get; set; }
  public string z { get; set; }
}

------解决方案--------------------
探讨

public ClassA
{
  public ClassB b{ get; set; }
}

public ClassB
{
  public string x { get; set; }  
  public string y { get; set; }
  public string z { get; set; }
}