Inserting Many-To-Many data in a database - asp.net-mvc

Question

I'm trying to add data to a Many-To-Many relationship.
Here's my controller
[HttpPost]
public ActionResult AddSkillsPost()
{
int Teacher_ID = Convert.ToInt32(Session["Teacher_ID"]);
var SkillsArray = Request.Form["chk_group[]"];
if(SkillsArray != null)
{
foreach(var skill in SkillsArray)
{
int Skill_ID = Convert.ToInt32(skill);
var SkillToBeModified = (from s in db.Skills
where s.ID == Skill_ID
select new Skill { ID = s.ID, SkillName = s.SkillName, Teachers = s.Teachers });
var Teacher = (from t in db.Teachers
where t.ID == Teacher_ID
select new Teacher { ID = t.ID, FirstName = t.FirstName, LastName = t.LastName,
Email = t.Email, Campus = t.Campus, Skills = t.Skills });
SkillToBeModified.Teachers.Add(Teacher);
db.Entry(SkillToBeModified).State = EntityState.Modified;
db.SaveChanges();
}
}
return RedirectToAction("MyProfile");
}
So I'm trying to add a teacher to a certain skill. However, I'm having a problem with this line
SkillToBeModified.Teachers.Add(Teacher);
I get the error
'IQueryable' does not contain a definition for 'Teachers' and
no extension method 'Teachers' accepting a first argument of type
'IQueryable' could be found (are you missing a using directive
or an assembly reference?)
I'm assuming this is a syntax mistake (something with the query?), but I can't figure out the correct way to write it.
Here's my model for Skills
[Table("Skills")]
public class Skill
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int ID { get; set; }
[Required]
public string SkillName { get; set; }
public virtual List<Teacher> Teachers { get; set; }
public Skill()
{
this.Teachers = new List<Teacher>();
}
}
and here's how my DB looks like
Looking forward to any reply's
EDIT: the form,
<form name="addSkillsForm" action="AddSkillsPost" method="post">
#foreach (var skill in Model.Skills)
{
<input type="checkbox" name="chk_group[]" value="#skill.ID" />#skill.SkillName< br />
}
<input type="submit" value="Update Skills" />
</form>
I'm using a check box form where users can check multiple items, maybe I'm not handeling them coorectly in my POST?

Answer 1

If your DB looks like the picture, you should be able to just do this.
[HttpPost]
public ActionResult AddSkillsPost()
{
int teacher_ID = Convert.ToInt32(Session["Teacher_ID"]);
var SkillsArray = Request.Form["chk_group[]"];
if (SkillsArray != null)
{
foreach (var skill in SkillsArray.Split(','))
{
int skill_ID = Convert.ToInt32(skill);
db.TeacherSkills.Add(new TeacherSkill() { Teacher_ID = teacher_ID, Skill_ID = skill_ID });
db.SaveChanges();
}
}
return RedirectToAction("MyProfile");
}
however if you're adding teacher to a skill then you'd do this.
[HttpPost]
public ActionResult AddSkillsPost()
{
var teacher_ID = Convert.ToInt32(Session["Teacher_ID"]);
var SkillsArray = Request.Form["chk_group[]"];
if (SkillsArray != null)
{
var teacher = db.Teachers.Find(teacher_ID);
foreach (var skill in SkillsArray.Split(','))
{
var skill_ID = Convert.ToInt32(skill);
var skillToBeModified = db.Skills.Find(skill_ID);
skillToBeModified.Teachers.Add(teacher);
db.Entry(skillToBeModified).State = EntityState.Modified;
db.SaveChanges();
}
}
return RedirectToAction("MyProfile");
}