Cant delete a primary key table

Question

Hi friends I have a table called Console and inside it contains one attribute called ConsoleName this is the ID of this table and the foreign key of two tables called Game and `Gamer. The problem that I am having is when I run the application everything works fine and I can insert all fine but when it comes to deleting a CONSOLE I cant delete any record when from the Console table as it gives me the following error:

Value cannot be null.
Parameter name: entity

I am using MVC3 C#

I tried the FOLLOWING:

[HttpPost, ActionName("Delete")]
    public ActionResult DeleteConfirmed(string id?)
    {            
        ConsoleTBL consoletbl = db.ConsoleTBLs.Find(id?);
        db.ConsoleTBLs.Remove(consoletbl);
        db.SaveChanges();
        return RedirectToAction("Index");
    }

But it does not work.

Please if you need anything let me know an I shall post what you ask for thanks

EDIT: Console Controller:

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Entity;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using MvcApplication1.Models;

namespace MvcApplication1.Controllers
{ 
    public class ConsoleController : Controller
    {
        private GameZoneEntities3 db = new GameZoneEntities3();

        //
        // GET: /Console/

        public ViewResult Index()
        {
            return View(db.ConsoleTBLs.ToList());
        }

        //
        // GET: /Console/Details/5

        public ViewResult Details(string id)
        {
            ConsoleTBL consoletbl = db.ConsoleTBLs.Find(id);
            return View(consoletbl);
        }

        //
        // GET: /Console/Create

        public ActionResult Create()
        {
            return View();
        } 

        //
        // POST: /Console/Create

        [HttpPost]
        public ActionResult Create(ConsoleTBL consoletbl)
        {
            if (ModelState.IsValid)
            {
                db.ConsoleTBLs.Add(consoletbl);
                db.SaveChanges();
                return RedirectToAction("Index");  
            }

            return View(consoletbl);
        }

        //
        // GET: /Console/Edit/5

        public ActionResult Edit(string id)
        {
            ConsoleTBL consoletbl = db.ConsoleTBLs.Find(id);
            return View(consoletbl);
        }

        //
        // POST: /Console/Edit/5

        [HttpPost]
        public ActionResult Edit(ConsoleTBL consoletbl)
        {
            if (ModelState.IsValid)
            {
                db.Entry(consoletbl).State = EntityState.Modified;
                db.SaveChanges();
                return RedirectToAction("Index");
            }
            return View(consoletbl);
        }

        //
        // GET: /Console/Delete/5

        public ActionResult Delete(string id)
        {
            ConsoleTBL consoletbl = db.ConsoleTBLs.Find(id);
            return View(consoletbl);
        }

        //
        // POST: /Console/Delete/5

        [HttpPost, ActionName("Delete")]
        public ActionResult DeleteConfirmed(string id)
        {            
            ConsoleTBL consoletbl = db.ConsoleTBLs.Find(id);
            db.ConsoleTBLs.Remove(consoletbl);
            db.SaveChanges();
            return RedirectToAction("Index");
        }

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

Index page of Console table:

@model IEnumerable<MvcApplication1.Models.ConsoleTBL>

@{
    ViewBag.Title = "Index";
}

<h2>Index</h2>

<p>
    @Html.ActionLink("Create New", "Create")
</p>
<table>
    <tr>
        <th>
            ConsoleID
        </th>
        <th></th>
    </tr>

@foreach (var item in Model) {
    <tr>
        <td>
            @Html.DisplayFor(modelItem => item.ConsoleID)
        </td>
        <td>
            @Html.ActionLink("Edit", "Edit", new { /* id=item.PrimaryKey */ }) |
            @Html.ActionLink("Details", "Details", new { /* id=item.PrimaryKey */ }) |
            @Html.ActionLink("Delete", "Delete", new { /* id=item.PrimaryKey */ })
        </td>
    </tr>
}

</table>

I have set the primary key on the actionlinks to "ConsoleID" but this did not work either just to tell you know what I have done

Answer 1

From the sound of it if you delete a Console you would orphan records in the Game and Gamer tables (which is not allows when a Foreign Key is enforced). So in order to delete a Console you'd either have to delete the other records using it as a foreign key or set the cascading behavior to do it for you.

Edit: However the errors you posted seems to imply you are missing a parameter. For deletes you will likely have two actions called Delete with one View. one Delete action will be a normal page request (typically to confirm the deletion) and the other will be the one requiring the postback (which you posted in your question).

The process will likely be something like this

Get /consoles/details/1

click the delete button

Get /consoles/delete/1

Press confirm or OK (which will be a submit button in a form)

Post /consoles/delete/1

Answer 2

Did you run this in debug mode and step into the delete method?

Did you check to make sure the consoletbl exists?

[HttpPost, ActionName("Delete")]
public ActionResult DeleteConfirmed(string id)
{            
    ConsoleTBL consoletbl = db.ConsoleTBLs.Find(id);

    if( consoletbl != null)
    {
        db.ConsoleTBLs.Remove(consoletbl);
        db.SaveChanges();
    }
    else
    {
        // should probably return an error message
        throw new ArgumentNullException("Could not find a console with the id of " + id);
    }
    return RedirectToAction("Index");
}

This should throw an exception if the id you are passing in is not found...

@model IEnumerable<MvcApplication1.Models.ConsoleTBL>

@{
    ViewBag.Title = "Index";
}

<h2>Index</h2>

<p>
    @Html.ActionLink("Create New", "Create")
</p>
<table>
    <tr>
        <th>
            ConsoleID
        </th>
        <th></th>
    </tr>

@foreach (var item in Model) {
    <tr>
        <td>
            @Html.DisplayFor(modelItem => item.ConsoleID)
        </td>
        <td>
            @Html.ActionLink("Edit", "Edit", new {  id=item.ConsoleID}) |
            @Html.ActionLink("Details", "Details", new {  id=item.ConsoleID}) |
            @Html.ActionLink("Delete", "Delete", new {  id=item.ConsoleID})
        </td>
    </tr>
}

</table>

I assume ConsoleID is the primary id so I replace "PrimaryKey" with this property. /* */ are used to put comments in your code and anything in between them will not be compiled