继承之调用基类构造函数知识点和思考练习（用了三层继承，重载了各层的构造函数，以期全面实验调用基类构造函数）

知识点

（二）调用基类构造函数
构造函数可以用于初始化新对象的数据成员。派生类的构造函数不仅要初始化本类中定义的数据成员，还要初始化从基类继承来的数据成员，因此，在创建派生类的实例时，应同时调用基类的构造函数，编译器会根据类的继承层次逐渐向上浏览整个上级类，找到最顶层的基类，先调用基类的构造函数，然后再依次调用各级派生类的构造函数。

 

思考练习

using System;
namespace NetNameSpace
{
    public class Net
    {
        private string netAddress;
        public Net()
        {
            netAddress = "www";
            Console.WriteLine("正在调用Net类不带参数的构造函数！netAddress被初始化为{0}", netAddress);
        }
        public Net(string netAddVar)
        {
            netAddress = netAddVar;
            Console.WriteLine("正在调用Net类带一个参数的构造函数！netAddress被初始化为{0}", netAddress);
        }
    }

    public class Blog : Net
    {
        private string blogName;
        public Blog()
            : base()
        {
            blogName = "Blog";
            Console.WriteLine("正在调用Blog类不带参数的构造函数！blogName被初始化为{0}", blogName);
        }
        public Blog(string blogNameVar)
            : base()
        {
            blogName = blogNameVar;
            Console.WriteLine("正在调用Blog类带一个参数的构造函数！blogName被初始化为{0}", blogName);
        }
        public Blog(string netAddVar, string blogNameVar)
            : base(netAddVar)
        {
            blogName = blogNameVar;
            Console.WriteLine("正在调用Blog类带两个参数的构造函数！blogName被初始化为{0}", blogName);
        }
    }

    public class ItBlog : Blog
    {
        private string category;
        public ItBlog()
            : base()
        {
            category = "IT category";
            Console.WriteLine("正在调用ItBlog类不带参数的构造函数！category被初始化为{0}", category);
        }
        public ItBlog(string cateVar)
            : base()
        {
            category = cateVar;
            Console.WriteLine("正在调用ItBlog类带一个参数的构造函数！category被初始化为{0}", category);
        }
        public ItBlog(string blogNameVar, string cateVar)
            : base(blogNameVar)
        {
            category = cateVar;
            Console.WriteLine("正在调用ItBlog类带两个参数的构造函数！category被初始化为{0}", category);
        }
        public ItBlog(string netAddVar, string blogNameVar, string cateVar)
            : base(netAddVar, blogNameVar)
        {
            category = cateVar;
            Console.WriteLine("正在调用ItBlog类带三个参数的构造函数！category被初始化为{0}", category);
        }
    }


    public class Program
    {
        static void Main()
        {
            Blog blog1 = new Blog();
            Blog blog2 = new Blog("CNBlogs");
            Blog blog3 = new Blog("www.cnblogs.com", "CNBlogs");
            Console.ReadLine();

            ItBlog itBlog1 = new ItBlog();
            ItBlog itBlog2 = new ItBlog("DOT NET");
            ItBlog itBlog3 = new ItBlog("CNBlogs", "DOT NET");
            ItBlog itBlog4 = new ItBlog("www.cnblogs.com", "CNBlogs", "DOT NET");
            Console.ReadLine();
        }
    }




}

输出结果

可见继承调用构造函数都是先调用最顶层的基类构造函数，再逐层往派生类调用