Question

我试图让我做的新学生阅读about方法，但是about方法中的变量表示它们没有被分配。我以为他们是因为我把它们设置为我制作的每个班级的默认值。

namespace studentHeirarchy
{
    class Program
    {
        static void Main(string[] args)
        {
            runStudent();   
        }
        static void runStudent()
        {
            Student one = new Student();
            Console.WriteLine(one.About());
            Console.ReadLine();
        }
    }
}

namespace studentHeirarchy
{
    public class ColumbiaStudent : Student
    {
        public bool isInOOP;

        public ColumbiaStudent()
        {
            isInOOP = true;
        }

        public String About()
        {
            string About = "my favorite course is OOP";
            return About;
        }

        public void GetOOPString()
        {
            throw new System.NotImplementedException();
        }
    }
}

namespace studentHeirarchy
{
    public class Student : Person
    {
        public int NumCourses;
        public string SchoolName;

        public Student()
        {
            NumCourses = 1;
            SchoolName = "Columbia";
        }

        public string About()
        {
            string About = string.Format("my name is{0}, I am {1} years old, I attend {2} and am taking {3} courses."),  Name, Age, SchoolName, NumCourses;
            return About;
        }

        public void AddCourse()
        {
            throw new System.NotImplementedException();
        }

        public void DropCourse()
        {
            throw new System.NotImplementedException();
        }
    }
}

namespace studentHeirarchy
{
    public class Person
    {
        public int Age;
        public string Name;

        public Person()
        {
            Age = 17;
            Name = "Jeff";
        }

        public string About()
        {
            throw new System.NotImplementedException();
        }
    }
}

Answer 1

您的问题出在string.Format上。您关闭了括号，然后它认为您正在声明其他变量：

string About = string.Format("my name is{0}, I am {1} years old, I attend {2} and am taking {3} courses."),  Name, Age, SchoolName, NumCourses;

应该是：

string About = string.Format("my name is{0}, I am {1} years old, I attend {2} and am taking {3} courses.",  Name, Age, SchoolName, NumCourses);

修复此问题会产生输出：

我的名字是杰夫，我17岁，我参加哥伦比亚大学并且正在修读1门课程。

另外，我建议你看一下C＃Polymorphism。这是另一个问题的核心，而其他所有人的答案都会受到影响。具体而言，您需要了解virtual，override和new（new，因为它与方法签名有关，而非实例化。）

Answer 2

你需要声明你的方法是虚拟的，在.net中，默认情况下它不是虚拟的。基本上，你隐藏了这个方法。

Answer 3

您没有调用父类的基础构造函数。 About方法也存在问题，必须是虚拟的，否则可能会调用错误的About。

以下是更正后的代码：

namespace studentHeirarchy
{
    class Program
    {
        static void Main(string[] args)
        {
            runStudent();   
        }
        static void runStudent()
        {
            Student one = new Student();
            Console.WriteLine(one.About());
            Console.ReadLine();
        }
    }
}

namespace studentHeirarchy
{
    public class ColumbiaStudent : Student
    {
        public bool isInOOP;

        public ColumbiaStudent() : base()
        {
            isInOOP = true;
        }

        public override String About()
        {
            string About = "my favorite course is OOP";
            return About;
        }

        public void GetOOPString()
        {
            throw new System.NotImplementedException();
        }
    }
}

namespace studentHeirarchy
{
    public class Student : Person
    {
        public int NumCourses;
        public string SchoolName;

        public Student() : base()
        {
            NumCourses = 1;
            SchoolName = "Columbia";
        }

        public override string About()
        {
            string About = string.Format("my name is{0}, I am {1} years old, I attend {2} and am taking {3} courses."),  Name, Age, SchoolName, NumCourses;
            return About;
        }

        public void AddCourse()
        {
            throw new System.NotImplementedException();
        }

        public void DropCourse()
        {
            throw new System.NotImplementedException();
        }
    }
}

namespace studentHeirarchy
{
    public class Person
    {
        public int Age;
        public string Name;

        public Person()
        {
            Age = 17;
            Name = "Jeff";
        }

        public virtual string About()
        {
            throw new System.NotImplementedException();
        }
    }
}

我怎么得到about方法来读取变量？

3 个答案: