Null viewmodel passed to controller - asp.net-core

Question

I have a basic 'create' view scaffolded from a domain model, so it is typed to the model
#model TblProduct
<form asp-controller="Product" asp-action="Create">
...
<input asp-for="Artist" class="form-control" />
...
I'm trying to add functionality and use a view model instead, and I'm starting with a very basic viewmodel with only that domain model within it:
public class ProductViewModel
{
public TblProduct P { get; set; }
}
Now I've changed the 'create' view to use the view model instead
#model ProductViewModel
<form asp-controller="Product" asp-action="Create">
...
<input asp-for="P.Artist" class="form-control" />
...
So I expect the model to be valid given that (aside from editing the variable names) I'm populating all the same fields from the form, and effectively no other fields have been added to the model.
An error occurs when I post the form, I pass a ProductViewModel parameter to the create method but on inspection it is null. However ModelState.IsValid is true. So the code tries to write to the db and fails.
public async Task<IActionResult> Create([Bind("ID,Artist,ProductTitle... (long list removed)...] ProductViewModel productAndItems)
{
var prod = productAndItems.P;
if (ModelState.IsValid)
{
_context.Add(prod);
...FAIL
Any idea what I should be checking here - what am I missing?
How do I get the view (typed to a viewmodel) to pass the model data to the controller? And if it's null, how can ModelState.IsValid be true? In the example above I have debugged, the parameter passed in productAndItems is null.

Answer 1

Your current Bind attribute is looking for the following properties ID,Artist,ProductTitle... (White-list) and it's not finding them so therefore it's ignore everything and treating it is as a (Black-list) item.
You can either decorate your ProductViewModel with the Bind attribute as follows:
[Bind(Include = "P")]
public class ProductViewModel
{
public TblProduct P { get; set; }
}
This will of course mean all the properties in the TblProduct will be bound when submitting
If you do not want all of the properties to be bound on submit for TblProduct then you can decorate the TblProduct with the Bind attribute as follows
public class ProductViewModel
{
public TblProduct P { get; set; }
}
[Bind(Include = "ID,Artist,ProductTitle")]
public class TblProduct
{
public int ID { get; set; }
public string Artist { get; set; }
public string ProductTitle { get; set; }
public string ProductSubTitle { get; set; } //we will not include this in our (White-list)
//more props
}
More reading at MSDN

Answer 2

you need to add a name attribute to your form so the controller will pick it up.