BindProperty attribute should support primary constructors with classes

[christiannagel]

Is there an existing issue for this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe the problem.

In an ASP.NET Core Razor project, creating this class with a primary constructor

public class Book(string title, string? publisher = default, int id = 0)
{
    public int Id { get; set; } = id;

    [StringLength(50)]
    public string Title { get; set; } = title;

    [StringLength(50)]
    public string? Publisher { get; set; } = publisher;
}

succeeds in scaffolding creating Razor pages with EF Core.

This is the code from the Create page code-behind:

public class CreateModel : PageModel
{
    private readonly RazorPagesWithEFCore.Data.BooksContext _context;

    public CreateModel(RazorPagesWithEFCore.Data.BooksContext context)
    {
        _context = context;
    }

    public IActionResult OnGet()
    {
        return Page();
    }

    [BindProperty]
    public Book Book { get; set; } = default!;

Running the application fails with an InvalidOperationException:

InvalidOperationException: Could not create an instance of type 'RazorPagesWithEFCore.Models.Book'. Model bound complex types must not be abstract or value types and must have a parameterless constructor. Record types must have a single primary constructor. Alternatively, set the 'Book' property to a non-null value in the 'RazorPagesWithEFCore.CreateModel' constructor.

Describe the solution you'd like

Using a parameterless constructor as described with the error, the application runs. I would prefer to use the primary constructor. Using records, the error mentions it's ok using a primary constructor. This should be possible with a class as well (and scaffolding creates code successfully).

Additional context

The alternative option mentioned in the error message "Alternatively, set the 'Book' property to a non-null value in the 'RazorPagesWithEFCore.CreateModel' constructor.", is not working. Assigning a non-null value to the Book property fails as well.