如果注释掉成员的构造函数调用，为什么我的程序不起作用？

Question

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

namespace ConsoleApplication8
{
    class Test
    {
        public StringBuilder a;

        /*public Test()
        {
            a = new StringBuilder();
        } */
    }

    class Program
    {
        static void Main(string[] args)
        {
            Test testobj = new Test();
            testobj.a.Append("Hello");
            Console.WriteLine(testobj.a);
            Console.ReadLine();
        }
    }
}

Shouldn't the default constructor for Test Class call every default constructor for every file in the class?

Answer 1

You seem to have a C++ background. You need to make sure that you understand object references in C# better. a is of reference type and is null initialized by default.