Using a foreign key in dropdown in mvc - asp.net-mvc-3

Question

I'm new to MVC, and stuck on what should be a pretty straight forward issue. I'm working through this tutorial and got everything pretty much working, except I now want to add a foreign key 'link' (not sure what it's called) but can't seem to get it to work. Here's what I have:
Tables:
Inventory:
Id | SerialNumber | ManufacturerId (foreignkey to Manufactueres->id)
Manufactureres
Id (primary key) | Name
Model (InventoryItem.cs):
public class InventoryItem {
public int Id {get; set; }
public int SerialNumber{ get; set; }
//this starts the trouble, I actually want to interact with the Manufactureres table -> Name column
public int ManufacturerId { get; set; }
}
View (Create.cshtml):
...
//What i really want is a dropdown of the values in the Manufactureres table
#Html.EditorFor(model=> model.ManufacturerId)
This must be a farely common issue when using a relational database there would be many foreign key relationships to be used/shown, but for some reason i can't find a tutorial or issue on stackoverflow that directly corresponds to something so simple. Any guidance, or direction is much appreciated!
Thanks,

Answer 1

I hope I understand your question correctly. Seems like when you want to add a new inventory item then you want a list of all the manufacturers in a dropdown list. I am going to work on this assumption, please let me know if I am off the track :)
Firstly go and create a view model. This view model you will bind to yout view. Never bind domain objects to your view.
public class InventoryItemViewModel
{
public int SerialNumber { get; set; }
public int ManufacturerId { get; set; }
public IEnumerable<Manufacturer> Manufacturers { get; set; }
}
Your domain objects:
public class InventoryItem
{
public int Id { get; set; }
public int SerialNumber{ get; set; }
public int ManufacturerId { get; set; }
}
public class Manufacturer
{
public int Id { get; set; }
public string Name { get; set; }
}
Your controller might look like this:
public class InventoryItemController : Controller
{
private readonly IManufacturerRepository manufacturerRepository;
private readonly IInventoryItemRepository inventoryItemRepository;
public InventoryItem(IManufacturerRepository manufacturerRepository, IManufacturerRepository manufacturerRepository)
{
// Check that manufacturerRepository and inventoryItem are not null
this.manufacturerRepository = manufacturerRepository;
this.inventoryItemRepository = inventoryItemRepository;
}
public ActionResult Create()
{
InventoryItemViewModel viewModel = new InventoryItemViewModel
{
Manufacturers = manufacturerRepository.GetAll()
};
return View(viewModel);
}
[HttpPost]
public ActionResult Create(InventoryItemViewModel viewModel)
{
// Check that viewModel is not null
if (!ModelState.IsValid)
{
Manufacturers = manufacturerRepository.GetAll()
return View(viewModel);
}
// All validation is cool
// Use a mapping tool like AutoMapper
// to map between view model and domain model
InventoryItem inventoryItem = Mapper.Map<InventoryItem>(viewModel);
inventoryItemRepository.Insert(inventoryItem);
// Return to which ever view you need to display
return View("List");
}
}
And then in your view you might have the following:
#model MyProject.DomainModel.ViewModels.InventoryItems.InventoryItemViewModel
<table>
<tr>
<td class="edit-label">Serial Number <span class="required">**</span></td>
<td>#Html.TextBoxFor(x => x.SerialNumber, new { maxlength = "10" })
#Html.ValidationMessageFor(x => x.SerialNumber)
</td>
</tr>
<tr>
<td class="edit-label">Manufacturer <span class="required">**</span></td>
<td>
#Html.DropDownListFor(
x => x.ManufacturerId,
new SelectList(Model.Manufacturers, "Id", "Name", Model.ManufacturerId),
"-- Select --"
)
#Html.ValidationMessageFor(x => x.ManufacturerId)
</td>
</tr>
</table>
I hope this helps :)

Answer 2

Yes, this is common issue, you need select Manufactureres in action and then send them to view. You can use ViewBag or strontly typed view model.
Examples:
Problem populating dropdown boxes in an ASP.NET MVC 3
Application
Having difficulty using an ASP.NET MVC ViewBag and
DropDownListfor
MVC3 Razor #Html.DropDownListFor

Answer 3

This is what I would recommend you.
1) Create a Manufacturer model class
public class Manufacturer
{
public int Id { get; set; }
public string Name { get; set; }
}
2) Create InventoryItem model class as follows
public class InventoryItem
{
public int Id { get; set; }
public int SerialNumber{ get; set; }
public int ManufacturerId { get; set; }
[ForeignKey("Id ")]
public Manufacturer Manufacturer{get; set;}
public IEnumerable<Manufacturer> Manufacturer {get;set;}
}
3) Make sure DbContext is also updated as follows
public DbSet<InventoryItem> InventoryItem {get;set;}
public DbSet<Manufacturer> Manufacturer{get;set;}
4) Controller
[HttpGet]
public ActionResult Create()
{
InventoryItem model = new InventoryItem();
using (ApplicationDbContext db = new ApplicationDbContext())
{
model.Manufacturer= new SelectList(db.Manufacturer.ToList(), "Id", "Name");
}
return View(model);
}
[HttpPost]
public ActionResult Create(InventoryItem model)
{
//Check the Model State
if(! ModelState.IsValid)
{
using (ApplicationDbContext db = new ApplicationDbContext())
{
model.Manufacturer= new SelectList(db.Manufacturer.ToList(), "Id", "Name");
return View(model);
}
}
using (ApplicationDbContext db = new ApplicationDbContext())
{
InventoryItem dto = new InventoryItem();
dto.SerialNumber= model.SerialNumber;
dto.Id= model.Id;
Manufacturer manudto = db.Manufacturer.FirstOrDefault(x => x.Id== model.Id);
dto.CatName = manudto.CatName;
db.Test.Add(dto);
db.SaveChanges();
}
TempData["SM"] = "Added";
return RedirectToAction("Index");
}
5) Make sure View has dropdownselect option in below format
<div class="form-group">
#Html.LabelFor(model => model.Name, htmlAttributes: new { #class = "control-label col-md-2" })
<div class="col-md-10">
#Html.DropDownListFor(model => model.Id, Model.Manufacturer,"Select", new { #class = "form-control" } )
#Html.ValidationMessageFor(model => model.Id, "", new { #class = "text-danger" })
</div>
</div>
Hope this works :D