How to implement the class - Student relationship in c#?

Question

I want to implement a system, which represents a ClassRoom- Student relationship. I want to impose the constraint that Each ClassRoom can have any number of students, but one student can be at only one ClassRoom.

I have created two classes - ClassRoom and Student. I have created a list in the Class ClassRoom.How do I ensure that no one can inser the same student in two classRooms.

By checking all the classrooms to ensure the student has not yet been inserted. — garryp, May 03 '15 at 19:25
If there are two subclasses classroom1 and classroom2, How do I iterate over all the objects? How do I get hold of all the class room objects ? — abhishek challa, May 03 '15 at 19:29
See my answer where classroom1 and classroom2 would be added to a list of ClassRoom objects. — garryp, May 03 '15 at 19:34

score 0 · Answer 1 · answered May 03 '15 at 19:33

0

In C# given an IEnumerable<ClassRoom> classRooms where ClassRoom has a property Students that is an IEnumerable<Student>

public bool HasStudent(Student student)
{
    return classRooms.Any(c => c.Students.Any(s => s == student));
}

answered May 03 '15 at 19:33

garryp

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score 0 · Accepted Answer · answered May 03 '15 at 20:18

I hope it is on your experience level:

ClassRoom

public class ClassRoom
{
    private List<Student> students = new List<Student>();

    public bool Contains(Student student)
    {
        return this.students.Contains(student);
    }

    public void Add(Student student)
    {
        if (!Contains(student))
            this.students.Add(student);
        student.StudentClassRoom = this;
    }

    public void Remove(Student student)
    {
        // if this contains, remove it anyway...
        if(Contains(student))
            this.students.Remove(student);

        // but do not set ClassRoom of student if she/he does not sit in this.
        if (student.StudentClassRoom != this)
            return;

        student.StudentClassRoom = null;
    }
}

Student

public class Student
{
    private ClassRoom stdClsRoom;
    public ClassRoom StudentClassRoom
    {
        get { return this.stdClsRoom; }
        set
        {
            if (value == this.stdClsRoom) //from null to null; from same to same;
                return;                   //do nothing

            if (this.stdClsRoom != null)  //if it set from something
            {
                ClassRoom original = this.stdClsRoom;
                this.stdClsRoom = null;  // set field to null to avoid stackoverflow
                original.Remove(this);   // remove from original
            }

            this.stdClsRoom = value;    // set field

            if (value != null)          //if it set to something
                value.Add(this);        // add to new
        }
    }
}

How to implement the class - Student relationship in c#?

2 Answers2