Missing something in "Delete" post method in MVC (EF 4.1)

Question

Following this example .. http://msdn.microsoft.com/en-us/data/gg685489

I am running into issues with Delete functionality.

[HttpPost]
public ActionResult Delete(int id, Blog blog)
{
    try
    {
        using (var db = new BlogDataEntities())
        {
            //Having issue here.. as soon as the next line is run in debug
            //mode .. it goes to catch.. and returns a view with null values.

            db.Entry(blog).State = System.Data.EntityState.Deleted;
            db.SaveChanges();
        }
        return RedirectToAction("Index");
    }
    catch
    {
        return View();
    }
}

In the parameters I checked 'blog' does not get the actual blog model that needs to be deleted. All the other methods work fine (Edit, Delete (get)..etc.. but Delete post fails. Am I missing something? thanks in advance for the help.

EDIT:

view code

@model DBFirstMVC.Models.Blog

@{
 ViewBag.Title = "Delete";
 }

  <h2>Delete</h2>

<h3>Are you sure you want to delete this?</h3>
<fieldset>
<legend>Blog</legend>

<div class="display-label">Title</div>
<div class="display-field">@Model.Title</div>

<div class="display-label">BloggerName</div>
<div class="display-field">@Model.BloggerName</div>
 </fieldset>
@using (Html.BeginForm()) {
  <p>
    <input type="submit" value="Delete" /> |
    @Html.ActionLink("Back to List", "Index")
  </p>
 }

EDIT 2: Non Razor Code in view:

<% using (Html.BeginForm()) { %>
<p>
    <input type="submit" value="Delete" /> |
    <%: Html.ActionLink("Back to List", "Index") %>
</p>
<% } %>

EDIT 3: (I tried in aspx)

<% using (Html.BeginForm()) { %>
<p>

    <%=Html.DisplayForModel();%> //Tried Html.EditorForModel also..
    <input type="submit" value="Delete" /> |
    <%: Html.ActionLink("Back to List", "Index") %>
</p>
<% } %>

FINAL EDIT (Corrected Solution)

@model DBFirstMVC.Models.Blog

@{
 ViewBag.Title = "Delete";
}

<h2>Delete</h2>

<h3>Are you sure you want to delete this?</h3>

@using (Html.BeginForm()) {
 <p>
<fieldset>
<legend>Blog</legend>

<div class="display-label">Title</div>
<div class="display-field">@Model.Title</div>

<div class="display-label">BloggerName</div>
<div class="display-field">@Model.BloggerName</div>

  <input type="submit" value="Delete" /> |
@Html.ActionLink("Back to List", "Index")
</fieldset>
</p>
}

Answer 1

The context probably doesn't have an Entry for your Blog because it isn't attached to the Context.

You probably need to retrieve the Blog first and then mark it as deleted using the Entry method:

[HttpPost]
public ActionResult Delete(int id, Blog blog)
{
    try
    {
        using (var db = new BlogDataEntities())
        {
            // retrieve the blog from the database
            var realBlog = db.Blogs.Find(blog.Id);

           // nothing to do here, just redirect
           if( realBlog == null )
                return RedirectToAction("Index");

          // since you have the entity just do this instead:
          db.Blogs.Remove(realBlog);
          db.SaveChanges();
        } 

        return RedirectToAction("Index");
    }
    catch( Exception )
    {
        return View();
    }
}

I don't really agree with the idea of using your entities as your models though. You should use View Models instead.

EDIT

Since you now are saying that Blog isn't being passed, try this:

@model Blog

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

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

You weren't actually giving the model binder any of the details it needed to construct your model.

Answer 2

is it possible to try the following:

[HttpPost]
public ActionResult Delete(Blog deletedBlog)
{
    try
    {
        using (var db = new BlogDataEntities())
        {
            // get blog entry from db context!!
            Blog blog = db.Blogs.Find(deletedBlog.Id);
            //Having issue here.. as soon as the next line is run in debug
            //mode .. it goes to catch.. and returns a view with null values.

            db.Entry(blog).State = System.Data.EntityState.Deleted;
            db.SaveChanges();
        }
        return RedirectToAction("Index");
    }
    catch(Exception e)
    {
        // should catch more specific exception
        // but catching 'e' should be a start
        return View();
    }
}

[Update] - pass in your Blog model from the view, tho as Dismissile says, you should really use a viewmodel, rather than the entity model for this purpose.

Also, you should catch the inner exception message and examine that for further clues.