c# - 多态性——练习

Question

好吧，这就是练习:

Define a class named student, containing three grades of students. The class will have a function that calculates the grades average. Now, define a class named student1 which will be derived from student and will add a function to calculate the sum of the grades.In the Main program, define a student variable and object of type student1. Perform placement of the object to variable and run the function of student1.

注意:这不是家庭作业，我是自己学习的。这是代码:

class Student
{
    protected int grade1, grade2, grade3;
    public Student(int grade1, int grade2, int grade3)
    {
        this.grade1 = grade1;
        this.grade2 = grade2;
        this.grade3 = grade3;
    }
    public double Average()
    {
        return (grade1 + grade2 + grade3) / 3;
    }
}
class Student1 : Student
{
    public Student1(int grade1, int grade2, int grade3)
        : base(grade1, grade2, grade3)
    {
    }
    public double Sum()
    {
        return grade1 + grade2 + grade3;
    }
}
class Program
{
    static void Main(string[] args)
    {
    }
}

我真的不知道在主课上该做什么，我该如何进行这个布置，而且，我想知道这样做有什么好处，如果到目前为止我有错误，请告诉我，非常感谢。

Answer 1

好的:我想这就是他们要找的东西，尽管英语有点生硬:

1) 声明学生变量

 Student s;

2) 声明Student1对象

 Student1 s1 = new Student1(1,2,3);

3) 执行对象到变量的放置:

s = s1;

4) 运行该函数(请注意，您必须将 s 转换为 Student1 类型才能访问类型特定的函数 Sum)

Console.WriteLine(((Student1)s).Sum());