CS5001 C# 程序不包含适合于入口点的静态 "Main" 方法

我写的代码长这个样，不知道为什么会出现标题上的这个错误，我按照百度的方法也试了，依旧是说 程序不包含适合于入口点的静态 "Main" 方法。我是该如何去改代码还是，如何去修改编译器的设置，求告知。
class Program
{
class Car
{
private double price;
private string pinpai;
private string xinghao;

    public double Price
    {
        get { return Price; }
        set
        {
            if (value > 0)
            {
                Price = value;
            }
            else
            {
                Price = 0;
            }
        }
    }

    public double Price1 { get => price; set => price = value; }
    public string Pinpai { get => pinpai; set => pinpai = value; }
    public string Xinghao { get => xinghao; set => xinghao = value; }
    
}
static void Main(string[] args)
{
    Car car1 = new Car();
    car1.Price1 = 20000;
    car1.Xinghao = "123";
    car1.Pinpai = "ab";

    Console.WriteLine(car1.Pinpai, car1.Xinghao, car1.Price1);

}

}

  //输出语句修改一下
  Console.WriteLine(car1.Pinpai, car1.Xinghao, car1.Price1);

Car 的定义移到 Program 定义之外

class Program
{
class Car
{
private double price;
private string pinpai;
private string xinghao;

    public double Price
    {
        get { return Price; }
        set
        {
            if (value > 0)
            {
                Price = value;
            }
            else
            {
                Price = 0;
            }
        }
    }
 
    public double Price1 { get => price; set => price = value; }
    public string Pinpai { get => pinpai; set => pinpai = value; }
    public string Xinghao { get => xinghao; set => xinghao = value; }
    
}
[STAThread]    //加个这个试试看
static void Main(string[] args)
{
    Car car1 = new Car();
    car1.Price1 = 20000;
    car1.Xinghao = "123";
    car1.Pinpai = "ab";
 
    Console.WriteLine(car1.Pinpai, car1.Xinghao, car1.Price1);
 
}
}