Question

My first MVC3 EF 4.2 site and I’m confused on some things, currently on ViewModels when querying and saving. Please correct me if I explain this poorly, i’m not sure how to term this. The .edmx automatically created the table classes but I read it was better to create a ViewModel, considering I need to join tables to display/edit my Product completely. The controller code below is where I join tables to output a Product to edit, and then save. My question – what is the right way to save the Product, to the Product.cs model generated by DbContext or my own ProductViewModel.cs?

Is there an easier method to query a product and join the tables and then map to the viewmodels parameters, or do I keep doing all this in the controller like below?

I also want to save/update the product each time someone views/clicks on the product, so I wasn’t sure if I create a separate ViewModel for updating just that parameter or again, use the Product model.

Hope that makes sense! I can explain further if needed.

private SiteForgeEntities db = new SiteForgeEntities();

public ActionResult Edit(int id)
    {
        var viewModel = (
            from a in db.Products
            join b in db.Sites
            on a.SiteId equals b.SiteId
            join c in db.Sections
            on a.SectionId equals c.SectionId
            join d in db.Affiliates
            on a.AffiliateId equals d.AffiliateId
            select new ProductViewModel()
            {
                ProductId = a.ProductId,
                Product = a.Product,
                Description = a.Description,
                Image = a.Image,
                Price = a.Price,
                Clicks = a.Clicks,
                Link = a.Link,        
                Site = b.Site,
                Section = c.Section,
                Affiliate = d.Affiliate
            }).Single(x => x.ProductId == id);      

        return View(viewModel);
    }

    [HttpPost]       
    public ActionResult Edit(Product product)
    {
     ...update database...do I pass in and save back to Product or my ProductViewModel
    }

Answer 1

You use ViewModel to pass multiple models to the view, but when you save data, you need to save it to the appropriate model. If you are adding or modifying products, you will add items to products (using your DbContext). If you have one-to-many relationship defined between two models (in your Product.cs model you might have a property declared as:

public virtual ICollection<SomeOtherModel> SomeOtherData { get; set; }

you can use this to build a table instead of passing everything in a ViewModel. There is a nice tutorial here regarding the CRUD operations using EF4. Have a look at these short tutorials that can give you an idea about your strategy http://www.asp.net/mvc/tutorials/getting-started-with-ef-using-mvc.