ModelState is false for relations with required fields - asp.net

Question

I have two models Invoice and Client which has one to many relation. My problem is when I try to create a new invoice the modelstate becomes false because the required fields of the Client object are not filled. I tried to set default values e.g. int property {get; set;} = 1; but this causes to override the property value when I try to retrieve the relational model. I'm new to asp.net any help would be appreciated.
Here is my Client model code:
public class Client
{
public int ClientId { get; set; }//Primary key
[Required]
[Display(Name = "Client/Company Name")]
public string Name { get; set; }
//.....
public List<Invoice> Invoices { get; set; }
}
Invoice Model:
public class Invoice
{
public int InvoiceId { get; set; }//Primary key
[Required]
[Display(Name = "Client/Company Name")]
public int ClientId { get; set; }//Foreign key
public Client client { get; set; }
//....
}
My code to save an invoice:
[HttpPost]//Save quote & redirect to edit quote
public IActionResult Create(Invoice quote)
{
ViewData["Title"] = "Create Quotation";//Set title of the view!
if (ModelState.IsValid)//If quote is validated to true.
{
_context.Invoices.Add(quote);//insert quote
_context.SaveChanges();
//Redirect to edit page to add items to the invoice
return RedirectToAction("Edit", new { id = quote.InvoiceId });
}
//...
}
My code to retrieve invoices with their client names
public IActionResult Index()
{
ViewData["Title"] = "Quotations";//Set title of the view!
//Return with array of all quotations.
return View(_context.Invoices.Include(i => i.client).Where(i => i.isQuote == true).ToArray());
}
Any hints or help would be appreciated.

Answer 1

Found a simpler solution:
Just add virtual keyword and GG
in Invoice Model:
public class Invoice
{
public int InvoiceId { get; set; }//Primary key
[Required]
[Display(Name = "Client/Company Name")]
public int ClientId { get; set; }//Foreign key
public virtual Client client { get; set; }
//....
}