一个简直class求解？

[ms2e]

class A里包含了class B，但是执行时出错，能不能帮忙改正一下？谢谢。


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

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
A test = new A();
test.b.data = "USD"; // ERROR
}
}

public class A
{
private B bField;

public B b
{
get { return this.bField ; }
set { this.bField = value; }
}

public A()
{
}
}

public class B
{
private string dataField;

public string data
{
get { return this.dataField; }
set { this.dataField = value; }
}
}

}

[panjf]

A类里的bField没有实例化。
public class A
{
private B bField = new B();

public B b
{
get { return this.bField ; }
set { this.bField = value; }
}

public A()
{
}
}

[達魔]

B在A里只是定义了，并未实例，new 一下应该就好了。

[達魔]

private B bField = new B();

[huangguangdou]

同意楼上的。

private B bField = new B();

[Eddie005]

或者改写成：
public class A
{
private B bField;

public B b
{
get { return (this.bField==null)?new B():this.bField ; }
set {
if(this.bField==null) this.bField=new B();
this.bField = value;
}
}

public A()
{
}
}

[songxiaozhao]

private B bField = new B();

[ms2e]

谢谢，解决了，感激