c# – Entity Framevork code first update a record in a table with a one-to-many relationship

Question:

Help to understand the problem.

I am trying to implement using entity framework code first to update a record in a table that is linked to another table with a many-to-one relationship.

Here are the data models

public class Defect
{
    public int id { get; set; }
    public string index { get; set; }
    public string specification { get; set; }
    public int amountOfBalls { get; set; }

    public virtual DefectCategory defectCategory { get; set; }
}


public class DefectCategory
{
    public int id { get; set; }
    public string index { get; set; }
    public string specification { get; set; }

    public virtual ICollection<Defect> defects { get; set; }
}

Here is the controller's GET method

    public ActionResult DefectEdit(int? id)
    {
        if (id == null)
        {
            return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
        }
        Defect defect = db.Defects.Find(id);
        if (defect == null)
        {
            return HttpNotFound();
        }
        ViewBag.defectCategory_id = new SelectList(db.DefectCategories, "id", "specification", defect.defectCategory.id);
        return View(defect);
    }

Here is the controller's POST method

    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult DefectEdit(Defect defect, int defectCategory_id)
    {
        if (ModelState.IsValid)
        {
            defect.defectCategory = db.DefectCategories.Find(defectCategory_id);
            db.Entry(defect).State = EntityState.Modified;
            db.SaveChanges();
            return RedirectToAction("ListDefects");
        }
        return View(defect);
    }

Here is a view

@using (Html.BeginForm())
{
@Html.AntiForgeryToken()

<div class="form-horizontal">
    <hr />
    <h4>Відредагувати існуючий дефект</h4>
    <hr />
    @Html.ValidationSummary(true, "", new { @class = "text-danger" })
    @Html.HiddenFor(model => model.id)

    <div class="form-group">
        @Html.LabelFor(model => model.index, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.index, new { htmlAttributes = new { @class = "form-control" } })
            @Html.ValidationMessageFor(model => model.index, "", new { @class = "text-danger" })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.defectCategory, "defectCategory_id", htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.DropDownList("defectCategory_id", null, htmlAttributes: new { @class = "form-control" })
            @Html.ValidationMessageFor(model => model.defectCategory, "", new { @class = "text-danger" })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.specification, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.specification, new { htmlAttributes = new { @class = "form-control" } })
            @Html.ValidationMessageFor(model => model.specification, "", new { @class = "text-danger" })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.amountOfBalls, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.amountOfBalls, new { htmlAttributes = new { @class = "form-control" } })
            @Html.ValidationMessageFor(model => model.amountOfBalls, "", new { @class = "text-danger" })
        </div>
    </div>

    <div class="form-group">
        <div class="col-md-offset-2 col-md-10">
            <input type="submit" value="Зберегти" class="btn btn-default" />
        </div>
    </div>
</div>
}

The problem is that all changed fields are updated in the database except for the defectCategory_id which is generated by the framework and I don't have access to it directly (or do I have it?) In one word, help me figure out how to correctly implement a one-to-many relationship in the controller and view

Answer:

public class Defect
{
    public int Id { get; set; }
    public string Index { get; set; }
    public string Specification { get; set; }
    public int AmountOfBalls { get; set; }

    //Предпочитаю создавать поля сам
    public int DefectCategoryId { get; set; }

    [ForeignKey("DefectCategoryId")] // указываю какое поле будет использоваться для связи
    public virtual DefectCategory DefectCategory { get; set; }
}

public class DefectCategory
{
    public int Id { get; set; }
    public string Index { get; set; }
    public string Specification { get; set; }

    public virtual ICollection<Defect> Defects { get; set; }
}

the Get and Post methods remain the same. Below is the full controller code:

public class HomeController : Controller
{
    public List<DefectCategory> DefectCategories = new List<DefectCategory>()
    {
        new DefectCategory(){Id = 1,Index="A", Specification = "дефекти паперу"},
        new DefectCategory(){Id = 2, Index="B", Specification="дефекти тексту"}
    };

    public List<Defect> Defects = new List<Defect>
    {
        new Defect(){Id=1, Index="A1", Specification="тест", AmountOfBalls = 10, DefectCategoryId = 1}
    };


    public ActionResult ListDefects()
    {
        return View(Defects);
    }

    public ActionResult DefectEdit(int? id)
    {
        if (id == null)
        {
            return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
        }
        var defect = Defects.Find(x=>x.Id==id);
        if (defect == null)
        {
            return HttpNotFound();
        }
        ViewBag.DefectCategories = new SelectList(DefectCategories, "id", "specification");
        return View(defect);
    }

    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult DefectEdit(Defect defect)
    {
        if (ModelState.IsValid)
        {
            //defect.defectCategory = db.DefectCategories.Find(defectCategory_id);
            return RedirectToAction("ListDefects");
        }
        return View(defect);
    }

edit view

@model WebApplication1.Controllers.Defect

@{
    ViewBag.Title = "DefectEdit";
}

<h2>DefectEdit</h2>


@using (Html.BeginForm())
{
    @Html.AntiForgeryToken()

    <div class="form-horizontal">
        <h4>Defect</h4>
        <hr />
        @Html.ValidationSummary(true, "", new { @class = "text-danger" })
        @Html.HiddenFor(model => model.Id)

        <div class="form-group">
            @Html.LabelFor(model => model.Index, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Index, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Index, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Specification, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Specification, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Specification, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.AmountOfBalls, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.AmountOfBalls, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.AmountOfBalls, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.DefectCategoryId, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.DropDownListFor(model => model.DefectCategoryId, (SelectList)ViewBag.DefectCategories, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.DefectCategoryId, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            <div class="col-md-offset-2 col-md-10">
                <input type="submit" value="Save" class="btn btn-default" />
            </div>
        </div>
    </div>
}

<div>
    @Html.ActionLink("Back to List", "Index")
</div>

@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
}

if you put a breakpoint in the post method, then we will see that defect.DefectCategoryId contains the key value that We selected