c# 出现An object reference is required 怎么回事啊，跟教学书上一模一样

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

namespace AutomobileClass
{

public class Automobile
{
private string type;
private string color;
private double price;
private bool isstart;

public Automobile(string type, string color, double price, bool isstart)
{
this.type = type;
this.color = color;
this.price = price;
this.isstart = isstart;
}

public void Automobileinfo()
{
if (Automobile.isstart == false) //这里出错
{
Console.WriteLine("品牌：{0}，颜色：{1}，价格：{2}，状态：停止", type, color, price);
}
if (Automobile.isstart == true) //这里出错
{
Console.WriteLine("品牌：{0}，颜色：{1}，价格：{2}，状态：行驶", type, color, price);
}
}
public void Start()
{
isstart = true;
}
public void Stop()
{
isstart = false;
}
}

class Program
{
static void Main(string[] args)
{
Automobile car1 = new Automobile("奥迪", "black", 50000, false);
Automobile car2 = new Automobile("桑塔纳", "red", 100000, true);
Console.WriteLine("车辆信息如下：\n");
car1.Automobileinfo();
car2.Automobileinfo();
Console.WriteLine();
Console.ReadKey();
}
}
}

isstart是类里的非静态字段，因此只需在方法中直接使用即可，如

public void Automobileinfo()
{
if (!isstart )
{
Console.WriteLine("品牌：{0}，颜色：{1}，价格：{2}，状态：停止", type, color, price);
}
if (isstart)
{
Console.WriteLine("品牌：{0}，颜色：{1}，价格：{2}，状态：行驶", type, color, price);
}
}

因为static void main(...)为静态方法。如果要在该方法内容访问change(...)方法，需要用static 关键字来修饰change(...)方法才可被访问，不然就会报lz帖出的异常。 public static myclass change(myclass m) { //...... }