Object oriented programming

You can see it this way: Not every Person is a Student but every Student is a Person, which mean every student have the attributes of being a student and a person. If you declare Claire as a Student Inherited from Person, you can access the Person and Students attributes but if you declare Claire as a Person, you can only access the Person attributes.

This is because a Student is special type of Person. Since it possesses any properties of that a Person has. But a Person may not be a Student. One example can be a Person may not take an exam. Here is a full inheritance article.Inheritance and behavioral subtyping[^].

BTW, The first concept is called LSP[^].

Person claire = new Student("Claire");
            claire.DescribeYourself();

This is one of S.O.L.I.D Software Engineering principle[^]

All the above Solutions do fair justice with the Topic. Let me put this with some technical example.

Lets declare a "Person" Class. In this class we have a method "DescribeYourself", which is declared as a "virtual", so that it's implementation can be Overriden in it's Child Classes.

public class Person
{
    private string PersonName;

    public Person() { }

    public Person(string personName)
    {
        PersonName = personName;
    }

    public virtual string DescribeYourself()
    {
          return "I am a Person. And my name is " + PersonName +".";    
    }

}

Now lets declare "Student" Class, inherited from "Person" Class. In this we have Overrided implementation of method "DescribeYourself".

public class Student: Person
{
    private string StudentName;

    public Student(string studentName)
    {
        StudentName = studentName;
    }

    public override string DescribeYourself()
    {
        return "I am a Student. And my name is " + StudentName + ".";
    }
}

Lets declare one more Class "Teacher", inherited from "Person" Class, In this also we have Overrided implementation of method "DescribeYourself".

public class Teacher : Person
{
    private string TeacherName;

    public Teacher(string teacherName)
    {
        TeacherName = teacherName;
    }


    public override string DescribeYourself()
    {
        return "I am a Teacher. And my name is " + TeacherName + ".";
    }

}

Now lets see Output of different Instantiations.

1) Firstly lets declare object of Class "Person", instantiated by the same Class.

string whoIAm = string.Empty;
Person someOne = null;

someOne = new Person("Claire");
whoIAm = someOne.DescribeYourself();

Result: I am a Person. And my name is Claire.

2) Now instantiate object of Class "Person" by Class "Student".

string whoIAm = string.Empty;
Person someOne = null;

someOne = new Student("Claire");
whoIAm = someOne.DescribeYourself();

Result: I am a Student. And my name is Claire.

3) Lets instantiate object of Class "Person" by Class "Teacher".

string whoIAm = string.Empty;
Person someOne = null;

someOne = new Teacher("Claire");
whoIAm = someOne.DescribeYourself();

Result: I am a Teacher. And my name is Claire.