How to represent many to many relation between student&class

ahmed salah

9y910.NET

Problem

I have two table Student and class many to many relationship

Student Table but i dont know how to represent Classroom_Student class in code .

Student Class
namespace UniversityData.Models
{
[Table("Student")]
public partial class Student
{
public Student()
{
this.Classes = new HashSet();
}
[DatabaseGenerated(DatabaseGeneratedOption.None)]
[Key]
public int StudentID { get; set; }
[Required]
[StringLength(50)]
public String StudentName { get; set; }
public ICollection Classes { get; set; }
}
}
ClassRoom Table
namespace UniversityData.Models
{
[Table("Class")]
public partial class Class
{
public Class()
{
this.Students = new HashSet();
}
[Key]
public int ClassID { get; set; }
[Required]
[StringLength(50)]
public string ClassName { get; set; }
public ICollection Students {get; set;}
}
}

Classroom_Student

StudID
ClassID
starttime
endtime
day
What i do as following
Create class for Student Table and class for ClassRoom Table
but Classroom_Student Table cannot do class for him
how to do class for Classroom_Student Table .

9 Replies

Know the answer? Post it — somebody with the same question will find it here.

Nitin Sontakke9y ago
Yes, unfortunately.

Otherwise there is no appropriate place to add additional instance properties. Because if you notice Student and ClassRoom classes are abstract. They cannot hold instance variables of actual class room getting filled with students every day. Hence the new class.

Hope it is clear enough!
ahmed salah9y ago
Thanks for reply
this meaning do separate class for Student_Class as student class and classroom class or what i do
Nitin Sontakke9y ago
Or better still...

public class Attendance
{
public ClassRoom classRoom {get; set;}
public List Students {get; set;}
public DateTime Started {get; set;}
public DateTime Finished {get; set;}
}
Nitin Sontakke9y ago
Got it. Here is a classic problem of instances. You have one Student. You have one Class Room. I think your question is every day that same student will go to that same class room and hence additional properties have now got added.

You will then need another class something like:

public class Attendance
{
public Student student {get; set;}
public ClassRoom classRoom {get; set;}
public DateTime Started {get; set;}
public DateTime Finished {get; set;}
}

Is this what you are looking for?
ahmed salah9y ago
Thank you i generated many to many between student and class
by fluent api code as following
protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {

            modelBuilder.Entity().
     HasMany(c => c.Students).
     WithMany(p => p.Classes).
     Map(
      m =>
      {
          m.MapLeftKey("ClassID");
          m.MapRightKey("StudentID");
          m.ToTable("Student_Class");
      });
}
Result of code will generate Table Student_Class with two fields
StudentID
ClassID
My Question here if i need to add more fields to Table Student_Class as
StartTime,EndTime
How to add and where is the place i will add
Nitin Sontakke9y ago
I notice you already did it, so where is the problem.
Nitin Sontakke9y ago
For junction tables, in my opinion, there will not be any separate classes, simply because of their nature.

If you just take your example, The student class can have collection of Class class as a property, for example:

public class Student
{
...
public List AttendsClasses {get; set;}
...
}

And Class class can have collection of Students class, as shown below:

public class Class
{
...
public List StudentsAttending {get; set;}
...
}

Hope you get the point.
ahmed salah9y ago
I attached my code with message
ahmed salah9y ago
Please every time i put my code within block and after i make post to my problem

i get text not organized as preview before post are this general problem

or there is my mistake

this is not first time i post topic or problem in forum

this problem in text organization are recently happen

so that if there are any problem from your side please tell me if possible