在数据库中插入多对多数据

Question

我正在尝试将数据添加到多对多关系。

这是我的控制器

[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");
}

所以我正在尝试为某项技能添加老师。但是，我对这一行有疑问

SkillToBeModified.Teachers.Add(Teacher);

我收到错误

'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?)

我假设这是一个语法错误（查询有什么问题？），但我想不出正确的写法。

这是我的技能模型

[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>();
    }
}

这是我的 DB 的样子

期待任何回复

编辑：表格，

<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>

我正在使用一个复选框表单，用户可以在其中选中多个项目，也许我没有在 POST 中正确处理它们？

Answer 1

如果您的数据库看起来像图片，您应该可以这样做。

[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");
}

但是，如果您要为一项技能添加教师，那么您会这样做。

[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");
}

在数据库中插入多对多数据

Inserting Many-To-Many data in a database

linq

asp.net-mvc

many-to-many

entity-framework