📓 3.4.0.7 Many-to-Many Update Functionality

We've added create and read functionality for our Tag entity and ItemTag join entity. Now we're ready to move onto adding update and delete functionality.

We won't add full CRUD for the ItemTag join entity, just CRD functionality. Instead of allowing users to update join relationships, we'll simply have them create or delete relationships.

The Tag entity on the other hand will have full CRUD functionality. So in this lesson we'll update our TagsController and views to have update functionality.

UPDATE: Adding Update Functionality to Tags

---

Let's start by creating Edit() GET and POST actions in the TagsController.cs.

Here's the new code we'll add:

Controllers/TagsController.cs

...

    public ActionResult Edit(int id)
    {
      Tag thisTag = _db.Tags.FirstOrDefault(tags => tags.TagId == id);
      return View(thisTag);
    }

    [HttpPost]
    public ActionResult Edit(Tag tag)
    {
      _db.Tags.Update(tag);
      _db.SaveChanges();
      return RedirectToAction("Index");
    }

...

The above code is the exact same as the code for update functionality in the CategoriesController: we pass the specific tag that we want to update to the view in the Edit() GET action, and then we update our database with the new tag in the Edit() POST action. When we're done, we redirect to the Index() action.

Next, let's create a view for our edit functionality. Within the Views/Tags/ subdirectory, create a new file called Edit.cshtml and add the following code:

Views/Tags/Edit.cshtml

@{
  Layout = "_Layout";
}

@model ToDoList.Models.Tag

<h2>Edit</h2>

<h4>Edit this tag: @Html.DisplayFor(model => model.Title)</h4>

@using (Html.BeginForm())
{
    @Html.HiddenFor(model => model.TagId)

    @Html.LabelFor(model => model.Title)
    @Html.EditorFor(model => model.Title)

    <input type="submit" value="Save" />
}

<p>@Html.ActionLink("Back to list", "Index")</p>

Finally, let's finish up by adding a link to our new Edit route to our tag's Details.cshtml:

Views/Tags/Details.cshtml

...
<p>@Html.ActionLink("Edit Tag", "Edit", new { id = Model.TagId })</p>

Now, if we run our application we should be able to edit tags. Up next, we'll add delete functionality for Tags and ItemTag join entities.