Store update, insert, or delete statement affected an unexpected number of rows (0).

Hi:

I have an application in which I have used the MVC Scaffolding to create and edit products.  The code works fine for creating and displaying products but when I try to edit the product, I get the following error:

Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. Refresh ObjectStateManager entries.

The model for the product is as follows:

[Bind(Exclude = "ProductId")]
    public class Product
    {
        [ScaffoldColumn(false)]
        public int ProductId { get; set; }

        [Required(ErrorMessage = "A Product Title is required")]
        [StringLength(160)]
        public string Title { get; set; }

        [Required(ErrorMessage = "Price is required")]
        [Range(0.00, 100.00,
            ErrorMessage = "Price must be between 0.00 and 100.00")]
        public decimal Price { get; set; }

        public string Description { get; set; }

        [DisplayName("Big Pic URL")]
        [StringLength(1024)]
        public string BigPicUrl { get; set; }

        [DisplayName("Small Pic URL")]
        [StringLength(1024)]
        public string SmallPicUrl { get; set; }

        
        public string ProductTypeCode { get; set; }
        public virtual ProductType ProductType { get; set; }

       
        public string ProductMakerCode { get; set; }
        public virtual ProductMaker ProductMaker { get; set; }
    }

 public class ProductMaker
    {
        [Key]
        [StringLength(8)]
        public string ProductMakerCode { get; set; }

        [DisplayName("Made By")]
        [StringLength(50)]
        public string Name { get; set; }
    }

 public class ProductType
    {

        [Key]
        [StringLength(8)]
        public string ProductTypeCode { get; set; }

        [StringLength(50)]
        [DisplayName("Type")]
        public string Name { get; set; }

        public string Description { get; set; }
        public List<Product> Products { get; set; }

    }

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The scaffolded code in the controller from MVC looks like this:
 public ActionResult Edit(int? id)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }
            Product product = db.Products.Find(id);
            if (product == null)
            {
                return HttpNotFound();
            }
            ViewBag.ProductMakerCode = new SelectList(db.ProductMakers, "ProductMakerCode", "Name", product.ProductMakerCode);
            ViewBag.ProductTypeCode = new SelectList(db.ProductTypes, "ProductTypeCode", "Name", product.ProductTypeCode);
            return View(product);
        }

        // POST: Products/Edit/5
        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Edit(Product product)
        {
            if (ModelState.IsValid)
            {
                db.Entry(product).State = EntityState.Modified;
                db.SaveChanges();
                return RedirectToAction("Index");
            }
            ViewBag.ProductMakerCode = new SelectList(db.ProductMakers, "ProductMakerCode", "Name", product.ProductMakerCode);
            ViewBag.ProductTypeCode = new SelectList(db.ProductTypes, "ProductTypeCode", "Name", product.ProductTypeCode);
            return View(product);
        }

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And the cshtml file is as follows:

@using (Html.BeginForm())
{
    @Html.AntiForgeryToken()
    
    <div class="form-horizontal">
        <h4>Product</h4>
        <hr />
        @Html.ValidationSummary(true, "", new { @class = "text-danger" })
        <div class="form-group">
            @Html.LabelFor(model => model.Title, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Title, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Title, "", new { @class = "text-danger" })
            </div>
        </div>

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

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

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Any suggestions on what to do to avoid this error greatly appreciated.

RBS
RBSAsked:
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SammyCommented:
In your Edit Action you should get the record first before attempting to save.
see my comment below as I am not sure what Entry refers to in your code
[HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Edit(Product product)
        {
            if (ModelState.IsValid)
            {
//You need to either attach or select the product first  before setting its state to Modified.
                db.Entry(product).State = EntityState.Modified;
                db.SaveChanges();
                return RedirectToAction("Index");
            }
            ViewBag.ProductMakerCode = new SelectList(db.ProductMakers, "ProductMakerCode", "Name", product.ProductMakerCode);
            ViewBag.ProductTypeCode = new SelectList(db.ProductTypes, "ProductTypeCode", "Name", product.ProductTypeCode);
            return View(product);
        }

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more about attach method in EF can be found here http://msdn.microsoft.com/en-us/data/jj592676.aspx
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RBSAuthor Commented:
Thanks Sammy - appreciate the link to EF as well

RBS
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