ASP.NET MVC : saving related entities on form submit - asp.net-mvc

Question

I require a little bit of help with ASP.NET MVC data entry. Can anybody help me how would I save a new product that is automatically tied to a catalog? It is a requirement that the product can not be created without a catalog. But I can save the product only without the catalog, and this is what I got so far:
Entities:
The Model:
public partial class Product
{
public Product()
{
this.ProductsInCatalog = new HashSet<ProductsInCatalog>();
}
public int Id { get; set; }
public string Code { get; set; }
public string Description { get; set; }
public virtual ICollection<ProductsInCatalog> ProductsInCatalog { get; set; }
}
public partial class Catalog
{
public Catalog()
{
this.ProductsInCatalog = new HashSet<ProductsInCatalog>();
}
public int Id { get; set; }
public string Code { get; set; }
public string Description { get; set; }
public virtual ICollection<ProductsInCatalog> ProductsInCatalog { get; set; }
}
public partial class ProductsInCatalog
{
public int ProductId { get; set; }
public int CatalogId { get; set; }
public virtual Product Product { get; set; }
public virtual Catalog Catalog { get; set; }
}
The Controller:
public ActionResult Create()
{
CatalogManager catalogManager = new CatalogManager();
ViewBag.Catalogs = catalogManager.GetCatalogs();
return View();
}
[HttpPost]
[ActionName("Save")]
public ActionResult Save(EURIS.Entities.Product product)
{
if (ModelState.IsValid)
{
ProductManager productManager = new ProductManager();
productManager.SaveProduct(product);
}
return RedirectToAction("Index");
}
The EFCore Manager:
public class ProductManager
{
readonly LocalDbEntities _context = new LocalDbEntities();
public List<Product> GetProducts()
{
var products = (from item in _context.Product select item).ToList();
return products;
}
public Product GetProductByID(int productID)
{
return _context.Product.SingleOrDefault(e => e.Id == productID);
}
public bool SaveProduct(Product product)
{
try
{
_context.Product.Add(product);
_context.SaveChanges();
return true;
}
catch (System.Exception exe)
{
return false;
}
}
public bool DeleteProduct(int productID)
{
try
{
Product product = _context.Product.SingleOrDefault(e => e.Id == productID);
_context.Product.Remove(product);
_context.SaveChanges();
return true;
}
catch (System.Exception exe)
{
return false;
}
}
public bool UpdateProduct(Product product)
{
try
{
Product prodToUpdate = _context.Product.Where(p => p.Id == product.Id).FirstOrDefault();
if (prodToUpdate != null)
{
_context.Entry(prodToUpdate).CurrentValues.SetValues(product);
_context.SaveChanges();
return true;
}
return false;
}
catch (System.Exception exe)
{
return false;
}
}
}
The View:
#model EURIS.Entities.Product
#{
ViewBag.Title = "Create";
Layout = "~/Views/Shared/_Layout.cshtml";
}
<h2>#ViewBag.Title</h2>
<p>
#Html.ActionLink("Back", "Index", "Product")
</p>
<table>
#using (Html.BeginForm("Save", "Product", FormMethod.Post))
{
<tr>
<td>Id</td>
<td>#Html.TextBoxFor(model => model.Id)</td>
<td>#Html.ValidationMessageFor(model => model.Id)</td>
</tr>
<tr>
<td>Code</td>
<td>#Html.TextBoxFor(model => model.Code)</td>
<td>#Html.ValidationMessageFor(model => model.Code)</td>
</tr>
<tr>
<td>Description</td>
<td>#Html.TextBoxFor(model => model.Description)</td>
<td>#Html.ValidationMessageFor(model => model.Description)</td>
</tr>
<tr>
<td>Catalog asoiation:</td>
<td>
<select id="ddlCatalog" onchange="onCatDdlChange">
#foreach (EURIS.Entities.Catalog cat in ViewBag.Catalogs)
{
<option value="#cat.Id">#cat.Code</option>
}
</select>
</td>
</tr>
<tr>
<td><button type="submit">Save</button></td>
</tr>
}
</table>