C#.MVC.Модели со связью многие ко многим

Создадим в базе 3 таблички – Students, Courses и коммутационную CourseStudent

Students

Courses

CourseStudent

В студии создадим их классы

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace modelsTraining2.Models
{
    public class Student
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Surname { get; set; }

        public virtual ICollection<Course> Courses { get; set; }
        public Student()
        {
            Courses = new List<Course>();
        }
    }
}

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

namespace modelsTraining2.Models

{

public class Student

{

public int Id { get; set; }

public string Name { get; set; }

public string Surname { get; set; }

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

public Student()

{

Courses = new List<Course>();

}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace modelsTraining2.Models
{
    public class Course
    {
        public int Id { get; set; }
        public string Name { get; set; }

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

        public Course()
        {
            Students = new List<Student>();
        }
    }
}

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

namespace modelsTraining2.Models

{

public class Course

{

public int Id { get; set; }

public string Name { get; set; }

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

public Course()

{

Students = new List<Student>();

}

И контекст, в который добавим коммутационную табличку

using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Web;

namespace modelsTraining2.Models
{
    public class StudentsContext:DbContext
    {
        public DbSet<Student> Students { get; set; }
        public DbSet<Course> Courses { get; set; }
        public StudentsContext() : base("DbConnection"){ }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Course>().HasMany(c => c.Students)
                .WithMany(s => s.Courses)
                .Map(t => t.MapLeftKey("CourseId")
                .MapRightKey("StudentId")
                .ToTable("CourseStudent")); 
        }
    }
}

using System;

using System.Collections.Generic;

using System.Data.Entity;

using System.Linq;

using System.Web;

namespace modelsTraining2.Models

{

public class StudentsContext:DbContext

{

public DbSet<Student> Students { get; set; }

public DbSet<Course> Courses { get; set; }

public StudentsContext() : base("DbConnection"){ }

protected override void OnModelCreating(DbModelBuilder modelBuilder)

{

modelBuilder.Entity<Course>().HasMany(c => c.Students)

.WithMany(s => s.Courses)

.Map(t => t.MapLeftKey("CourseId")

.MapRightKey("StudentId")

.ToTable("CourseStudent"));

}

Далее, создадим контроллер и представления по шаблону CRUD

Правой кнопкой на контроллере -> Add

Вот какой код получится у нас для контроллера

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Entity;
using System.Linq;
using System.Threading.Tasks;
using System.Net;
using System.Web;
using System.Web.Mvc;
using modelsTraining2.Models;

namespace modelsTraining2.Controllers
{
    public class StudentsController : Controller
    {
        private StudentsContext db = new StudentsContext();

        // GET: Students
        public async Task<ActionResult> Index()
        {
            return View(await db.Students.ToListAsync());
        }

        // GET: Students/Details/5
        public async Task<ActionResult> Details(int? id)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }
            Student student = await db.Students.FindAsync(id);
            if (student == null)
            {
                return HttpNotFound();
            }
            return View(student);
        }

        // GET: Students/Create
        public ActionResult Create()
        {
            return View();
        }

        // POST: Students/Create
        // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
        // more details see https://go.microsoft.com/fwlink/?LinkId=317598.
        [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<ActionResult> Create([Bind(Include = "Id,Name,Surname")] Student student)
        {
            if (ModelState.IsValid)
            {
                db.Students.Add(student);
                await db.SaveChangesAsync();
                return RedirectToAction("Index");
            }

            return View(student);
        }

        // GET: Students/Edit/5
        public async Task<ActionResult> Edit(int? id)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }
            Student student = await db.Students.FindAsync(id);
            if (student == null)
            {
                return HttpNotFound();
            }
            return View(student);
        }

        // POST: Students/Edit/5
        // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
        // more details see https://go.microsoft.com/fwlink/?LinkId=317598.
        [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<ActionResult> Edit([Bind(Include = "Id,Name,Surname")] Student student)
        {
            if (ModelState.IsValid)
            {
                db.Entry(student).State = EntityState.Modified;
                await db.SaveChangesAsync();
                return RedirectToAction("Index");
            }
            return View(student);
        }

        // GET: Students/Delete/5
        public async Task<ActionResult> Delete(int? id)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }
            Student student = await db.Students.FindAsync(id);
            if (student == null)
            {
                return HttpNotFound();
            }
            return View(student);
        }

        // POST: Students/Delete/5
        [HttpPost, ActionName("Delete")]
        [ValidateAntiForgeryToken]
        public async Task<ActionResult> DeleteConfirmed(int id)
        {
            Student student = await db.Students.FindAsync(id);
            db.Students.Remove(student);
            await db.SaveChangesAsync();
            return RedirectToAction("Index");
        }

        protected override void Dispose(bool disposing)
        {
            if (disposing)
            {
                db.Dispose();
            }
            base.Dispose(disposing);
        }
    }
}

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using System;

using System.Collections.Generic;

using System.Data;

using System.Data.Entity;

using System.Linq;

using System.Threading.Tasks;

using System.Net;

using System.Web;

using System.Web.Mvc;

using modelsTraining2.Models;

namespace modelsTraining2.Controllers

{

public class StudentsController : Controller

{

private StudentsContext db = new StudentsContext();

// GET: Students

public async Task<ActionResult> Index()

{

return View(await db.Students.ToListAsync());

}

// GET: Students/Details/5

public async Task<ActionResult> Details(int? id)

{

if (id == null)

{

return new HttpStatusCodeResult(HttpStatusCode.BadRequest);

}

Student student = await db.Students.FindAsync(id);

if (student == null)

{

return HttpNotFound();

}

return View(student);

}

// GET: Students/Create

public ActionResult Create()

{

return View();

}

// POST: Students/Create

// To protect from overposting attacks, please enable the specific properties you want to bind to, for

// more details see https://go.microsoft.com/fwlink/?LinkId=317598.

[HttpPost]

[ValidateAntiForgeryToken]

public async Task<ActionResult> Create([Bind(Include = "Id,Name,Surname")] Student student)

{

if (ModelState.IsValid)

{

db.Students.Add(student);

await db.SaveChangesAsync();

return RedirectToAction("Index");

}

return View(student);

}

// GET: Students/Edit/5

public async Task<ActionResult> Edit(int? id)

{

if (id == null)

{

return new HttpStatusCodeResult(HttpStatusCode.BadRequest);

}

Student student = await db.Students.FindAsync(id);

if (student == null)

{

return HttpNotFound();

}

return View(student);

}

// POST: Students/Edit/5

// To protect from overposting attacks, please enable the specific properties you want to bind to, for

// more details see https://go.microsoft.com/fwlink/?LinkId=317598.

[HttpPost]

[ValidateAntiForgeryToken]

public async Task<ActionResult> Edit([Bind(Include = "Id,Name,Surname")] Student student)

{

if (ModelState.IsValid)

{

db.Entry(student).State = EntityState.Modified;

await db.SaveChangesAsync();

return RedirectToAction("Index");

}

return View(student);

}

// GET: Students/Delete/5

public async Task<ActionResult> Delete(int? id)

{

if (id == null)

{

return new HttpStatusCodeResult(HttpStatusCode.BadRequest);

}

Student student = await db.Students.FindAsync(id);

if (student == null)

{

return HttpNotFound();

}

return View(student);

}

// POST: Students/Delete/5

[HttpPost, ActionName("Delete")]

[ValidateAntiForgeryToken]

public async Task<ActionResult> DeleteConfirmed(int id)

{

Student student = await db.Students.FindAsync(id);

db.Students.Remove(student);

await db.SaveChangesAsync();

return RedirectToAction("Index");

}

protected override void Dispose(bool disposing)

{

if (disposing)

{

db.Dispose();

}

base.Dispose(disposing);

}

А вот вьюшечку для Details поправим таким образом

@model modelsTraining2.Models.Student

@{
    ViewBag.Title = "Details";
}

<h2>Details</h2>

<div>
    <h4>Student</h4>
    <hr />
    <dl class="dl-horizontal">
        <dt>
            @Html.DisplayNameFor(model => model.Name)
        </dt>

        <dd>
            @Html.DisplayFor(model => model.Name)
        </dd>

        <dt>
            @Html.DisplayNameFor(model => model.Surname)
        </dt>

        <dd>
            @Html.DisplayFor(model => model.Surname)
        </dd>
        <dt>Courses</dt>

        <dd>

            @foreach (var c in Model.Courses)
            {
                <p>@c.Name </p>
            }

        </dd>

    </dl>
</div>
<p>
    @Html.ActionLink("Edit", "Edit", new { id = Model.Id }) |
    @Html.ActionLink("Back to List", "Index")
</p>

@model modelsTraining2.Models.Student

ViewBag.Title = "Details";

}

<h2>Details</h2>

<div>

<h4>Student</h4>

<hr />

<dt>

@Html.DisplayNameFor(model => model.Name)

</dt>

<dd>

@Html.DisplayFor(model => model.Name)

</dd>

<dt>

@Html.DisplayNameFor(model => model.Surname)

</dt>

<dd>

@Html.DisplayFor(model => model.Surname)

</dd>

<dt>Courses</dt>

<dd>

@foreach (var c in Model.Courses)

{

}

</dd>

</dl>

</div>

<p>

@Html.ActionLink("Edit", "Edit", new { id = Model.Id }) |

@Html.ActionLink("Back to List", "Index")

</p>

Добавим туда перечисления, курсы…

        <dt>Courses</dt>

        <dd>

            @foreach (var c in Model.Courses)
            {
                <p>@c.Name </p>
            }

        </dd>

<dt>Courses</dt>

<dd>

@foreach (var c in Model.Courses)

{

}

</dd>

Курсы у нас отобразились. Что будем делать дальше?

Изменение метода Edit

Напишем метод Edit2

Метод после шаблонов CRUD дает возможность изменить только имя и фамилию, поэтому нам нужно изменить контроллер и представление таким образом, чтобы мы могли поменять курсы, сделаем это следующим образом

public ActionResult Edit2(int id = 0)
        {
            Student student = db.Students.Find(id);
            if (student == null)
            {
                return HttpNotFound();
            }
            ViewBag.Courses = db.Courses.ToList();
            return View(student);
        }

        [HttpPost]
        public ActionResult Edit2(Student student, int[] selectedCourses)
        {
            Student newStudent = db.Students.Find(student.Id);
            newStudent.Name = student.Name;
            newStudent.Surname = student.Surname;

            newStudent.Courses.Clear();
            if (selectedCourses != null)
            {
                //получаем выбранные курсы
                foreach (var c in db.Courses.Where(co => selectedCourses.Contains(co.Id)))
                {
                    newStudent.Courses.Add(c);
                }
            }

            db.Entry(newStudent).State = EntityState.Modified;
            db.SaveChanges();
            return RedirectToAction("Index");
        }

public ActionResult Edit2(int id = 0)

{

Student student = db.Students.Find(id);

if (student == null)

{

return HttpNotFound();

}

ViewBag.Courses = db.Courses.ToList();

return View(student);

}

[HttpPost]

public ActionResult Edit2(Student student, int[] selectedCourses)

{

Student newStudent = db.Students.Find(student.Id);

newStudent.Name = student.Name;

newStudent.Surname = student.Surname;

newStudent.Courses.Clear();

if (selectedCourses != null)

{

//получаем выбранные курсы

foreach (var c in db.Courses.Where(co => selectedCourses.Contains(co.Id)))

{

newStudent.Courses.Add(c);

}

db.Entry(newStudent).State = EntityState.Modified;

db.SaveChanges();

return RedirectToAction("Index");

}

C#.MVC.Модели со связью многие ко многим

Изменение метода Edit

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