很简单的c#程序，我不知错在哪里?能不能指点一下阿

Question

我是初学者 请指教using System;
namespace p3_2
{
    //定义一个class类对象
    public class info
    {
        public string name;
        public int age;
        public string tel;
        public class address
        {
            public string m_city;
            public string m_street;
            public int m_number;
        }
        public address m_address;
    }
    //类的实现
    public class classsample
    {
        public static void Main()
        {
            info c1 = new info();
            c1.name = "owen";
            c1.age = 21;
            c1.tel = "3423423";
            c1.m_address.m_city = "利物浦";  //提示说错在这一条
            c1.m_address.m_street = "安菲尔德";
            c1.m_address.m_number = 10;
            Console.WriteLine(c1.name);
            Console.WriteLine(c1.age);
            Console.WriteLine(c1.tel);
            Console.WriteLine(c1.m_address.m_city);
            Console.WriteLine(c1.m_address.m_street);
            Console.WriteLine(c1.m_address.m_number);        }
    }
}

Answer 1

对于m_address的实例化，您没有做好，info c1 = new info();做了实例化，可是在info类中的address子类您并没有实例化，所以提示出错

Answer 2

public class info
    {
        public string name;
        public int age;
        public string tel;
        public class address
        {
            public string m_city;
            public string m_street;
            public int m_number;
        }
        public address m_address;
    }
我觉得错误在你在类中又定义了一个类address，应该是struct吧。粗心的可能。