Updating model after HttpPost

I want to update existing Product objects in database by images, but image goes to DB successfully only when i create new objects.

I'm trying to update my object this way

[HttpPost]
public ActionResult Edit(Product product, HttpPostedFileBase image)
    {

    if开发者_如何学C (ModelState.IsValid)
        {
            if (image != null)
            {
                product.ImageMimeType = image.ContentType;
                product.ImageData = new byte[image.ContentLength];
                image.InputStream.Read(product.ImageData, 0, image.ContentLength);
            }
            if (product.ProductID != 0)
                UpdateModel<Product>(repository.Products.FirstOrDefault(p => p.ProductID == product.ProductID));
            repository.SaveProduct(product);
            TempData["message"] = string.Format("{0} has been saved", product.Name);
            return RedirectToAction("Index");
        }
        return View(product);
    }
//repository.SaveProduct()


public void SaveProduct(Product product)
        {

    if (product.ProductID == 0)
            {
                context.Products.Add(product);
            }
            context.SaveChanges();
        }

The View @ Upload new image: input type="file" name="Image" input type="submit" value="Save" @Html.ActionLink("Cancel and return to List", "Index") }

I noticed you were read the "Pro ASP.NET MVC 3 Framework" and meet this issue same to me.

The author had a error at here, the code should be(You must reference and using the System.Data.Entity namespace at first):

    public void SaveProduct(Product product)
    {
        if (product.ProductID == 0)
        {
            context.Products.Add(product);
        }
        else
        {
            context.Entry(product).State = System.Data.EntityState.Modified;
        }

        context.SaveChanges();
    }

This is all kinds of wrong.

You should be using specific ViewModels for your Edit and Create actions.

Define a separate class containing the properties you wish to edit and any UI validation:

public class EditProductViewModel {
    [HiddenInput]
    public int Id {get;set;}
    [Required]
    public string Name {get;set;}
    [Required]
    public string Description {get;set;}
    public HttpPostedFileBase Image {get;set;}
}

Then change your action method like so:

[HttpPost]
public ActionResult Edit(EditProductViewModel viewModel) {
    if (ModelState.IsValid) {
        var product = repository.Products.FirstOrDefault(p => p.Id == viewModel.Id);
        // TODO - null check of product
        // now lefty righty
        product.Name = viewModel.Name;
        product.Description = viewModel.Description;

        if (viewModel.Image.ContentLength > 0) {
            product.ImageMimeType = image.ContentType; //  wouldn't trust this (better to lookup based on file extension)                
            product.ImageData = new byte[image.ContentLength];                 
            image.InputStream.Read(product.ImageData, 0, image.ContentLength); 
        }

        repository.SaveProduct(product);
        return RedirectToAction("Index");
    }

    return View(viewModel);
}

Here's a good post discussing the ViewModel pattern.

Try doing this

context.Products.Attach(product);

Note: only when doing the update, not when inserting a new product.

Try this:

public void SaveProduct(Product product)
{
    if (product.ProductID == 0)
    {
        context.Products.Add(product);
    }
    else    // Update operation
    {
        context.Products.Attach(product);
    }
    context.SaveChanges();
}

Note: I would change the way you determine which is it a new or an updated product.

[HttpPost]

public RedirectToRouteResult Save(TestViewModel viewModel)

{

TempData["Output"] = "Here is some response";
return RedirectToAction("Index", viewModel);

}