根据MVC操作结果更新关系数据库数据（实体框架）

Question

I'm trying to update a table within my DB to change a particular relationship based on a user selecting a card, and then click a button to send that card to that deck, see below:

My Models:

public class Card
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int? Atk { get; set; }
    public int? Def { get; set; }
    public string Desc {get; set;}
    public int? Level { get; set; }
    public string Type { get; set; }
    public string Attribute { get; set; }
    [DisplayName("Image")]
    public virtual List<Image> Card_Images { get; set; }

    public virtual List<Deck> Deck { get; set; }


}



    public class Deck
    {
        public int id { get; set; }

        public string Name { get; set; }

        public string Notes { get; set; }
        [DisplayName("Card")]
        public virtual List<Card> Card { get; set; }
    }

My Controller action:

    public ActionResult AddToDeck(int id)
    {
        var cardInDb = _context.Cards.Single(c => c.Id == id);

        var deckInDb = _context.Decks.Single(d => d.id == id);

        foreach (var c in cardInDb.Deck)
        {
            cardInDb.Id = deckInDb.id;
        }


        _context.SaveChanges();

        return View("Index");
    }

My View:

@using YGOBuilder.Controllers
@model YGOBuilder.Models.Card

<div>
    <h4>Card</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.Atk)
        </dt>

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

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

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

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

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

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

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

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

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

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

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

        @foreach (var item in Model.Card_Images)
        {

            <td>
                <img src=@item.image_url height="300" width="200" style="margin: 2px">
            </td>

        }


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

The DB Table I'm trying to manipulate looks as follows there is no model attached to this, this was created by Entity Framework for a many to many relationship:

DeckCards
    (key sign) Deck_id
    (key sign) Card_id

I want to somehow display a list of all current decks in the view above, would I need to create a viewModel for this?

Also, what is the best approach for when the user is viewing a card with an id of 1, they then want to update the DeckCards table to pair that card with a deck of id 3, eg

 Deck_Id     Card_Id
    3            1

Answer 1

I think your controller action is going to make all the cards in the deck the same. You have the following:

foreach (var c in cardInDb.Deck)
{
    cardInDb.Id = deckInDb.id;
}

Instead, try:

deckInDb.Card.Add(cardInDb);
cardInDb.Deck.Add(deckInDb);

Unless I'm misunderstanding your goal, when you call SaveChanges(), the DB should get the appropriate updates.