How to Insert checkbox checked values id in Many to Many relationship table?

Question

I wanted to add the value of checkbox ids to many to many relation table between two tables Course-Student

i have 3 tables Course{ CourseID,CourseName }, Studdent{StudentID,StudentName} and CourseStudet{CourseID, StudentID} Course table already have course{1.DataScience,2.English,3.Physics} while Inserting Student i have shown course checkboxes with these options fetching list of these courses from database to show in view to user when he is about to register now i am confused how to insert into database?

public class CourseModel {

        public List<Course> mycourse{ get; set; }

        public string StudentName {get; set;}


    }

EF generated Class

 public partial class Course
    {
        public Course()
        {
            this.Student= new HashSet<Student>();
        }

        public int CourseID { get; set; }
        public string CourseName { get; set; }

        i have inserted this field to check for checked value
        public bool Ischecked { get; set; }

        public virtual ICollection<Student> Student { get; set; }
    }


 public partial class Student
    {

        public Student()
        {
            this.Course= new HashSet<Course>();
        }

        public int StudentID { get; set; }
        public string StudentName { get; set; }


        public virtual ICollection<Course> Course{ get; set; }
    }

 public ActionResult Index()
        {
            CourseModel coursemodel = new CourseModel();
            using (Entities db = new Entities())
            {
                coursemodel.mycourse = db.Course.ToList<Course>();

                 return View(coursemodel);

            }


        }
        [HttpPost]
        public ActionResult Index(CourseModel course)
        {       
            return View(course);
        }

View

@using (Html.BeginForm("index", "Course", FormMethod.Post))

         <input type="Text" name="StudentName" placeholder="Name" />

{
    <table>
        @for (int i = 0 ; i < Model.mycourse.Count; i++)
        {
            if (i % 3 == 0) {
                @:<tr></tr>
            }
        <div>

            @Html.CheckBoxFor(x => x.mycourse[i].Ischecked)
            <label>@Model.mycourse[i].CourseName</label>
            @Html.HiddenFor(x => x.mycourse[i].CourseID)
            @Html.HiddenFor(x => x.mycourse[i].CourseName)
        </div>



        }

    </table>
   <input type="submit" value="Submit" />
}

i am getting checkbox id,name and which course is checked now how can i add student with including these values to relationship table CourseStudent ?

Answer 1

You have problems with your database design. Remove ischecked field.Remember while you are designing entities, you shouldn't put fields that are for view. It is like that I make Reports table from my each query.

correct your models

  public partial class Course
{
    public Course()
    {
        this.Student = new HashSet<Student>();
    }

    public int CourseID { get; set; }
    public string CourseName { get; set; }

    public virtual ICollection<Student> Student { get; set; }
}


public partial class Student
{

    public Student()
    {
        this.Course = new HashSet<Course>();
    }

    public int StudentID { get; set; }
    public string StudentName { get; set; }

    public virtual ICollection<Course> Course { get; set; }
}

Add viewmodels(You can use view models for showing custom data for your view) You can read more

ViewModel

public class CourseViewModel
{
    public Course course { get; set; }
    public bool CheckBox { get; set; }
}

public class StudentCourseViewModel
{
    public List<CourseViewModel> coursesVM { get; set; }
    public Student student { get; set; }
}

Controller

  public ActionResult index()
  {
      Entities db = new Entities();
      List<CourseViewModel> courselist = new List<CourseViewModel>();
      foreach (var item in db.Course.ToList())
        {
            courselist.Add(new CourseViewModel { course = item});
        }
      StudentCourceViewModel model = new StudentCourseViewModel(
      {
          student = new student(),
          coursesVM = courselist   }
      };
      return View(model);
  }
  [HttpPost]
  public ActionResult Save(StudentCourseViewModel model)
  {
      Entities db = new Entities();
      Student stdindb = db.Students.FirstorDefault(c => c.StudentName == model.student.StudentName); 
      if(stdindb == null)
      {
       stdindb = new student(){//your properties};
       db.students.add(stdindb);
      }
      foreach (var item in model.coursesVM)
      {
        if (item.Ischecked)
          {
            stdindb.Course.Add(db.course.single(c=>c.CourseId == item.course.CourseId ));
          }
        }
        db.SaveChanges();
        return View();
  }

View

@model SchoolCMS.Models.StudentCourseViewModel
@{
    ViewBag.Title = "Select Course";
}

@using (Html.BeginForm("Save", "home", FormMethod.Post))
{
@Html.TextBoxFor(c=>c.student.StudentName)
<table>
    @for (int i = 0; i < Model.coursesVM.Count; i++)
    {
        <tr>
            <td>
            @Html.CheckBoxFor(c => c.coursesVM[i].Ischecked)
            @Html.HiddenFor(c => c.coursesVM[i].course.CourseID)
        </td>
        <td>@Html.DisplayFor(c => c.coursesVM[i].course.CourseName)</td>
    </tr>
    }
    </table>
    <input type="submit" value="Submit" />
}