What am I doing wrong?

I have not used ASP.NET Core or EF Core in a long time so I’m relatively new to it.

When I debug with breakpoints in the OnPost the Items list has data, but when the page is redirected and loads the Items is null.

I am using EF Core in-memory to store the data, it’s mostly a simple page but I can’t seem to get it to work.

Any help much appreciated.

These are my model classes:

[PrimaryKey("OrderId")]
public class Request
{
    public string? OrderId { get; set; }
    public string? SalesPerson { get; set; }
    public string? OrderConfirmedDate { get; set; }
    public string? CurrencyName { get; set; }
    public string? SpecialInstructions { get; set; }
    public string? InvoiceAdvertiser { get; set; }
    public string? InvoiceCompanyName { get; set; }
    public string? InvoiceAddress1 { get; set; }
    public string? InvoiceAddress2 { get; set; }
    public string? InvoiceAddress3 { get; set; }
    public string? InvoiceCity { get; set; }
    public string? InvoiceStateCounty { get; set; }
    public string? InvoicePostCode { get; set; }
    public string? InvoiceCountryName { get; set; }
    public string? InvoiceContactName { get; set; }
    public string? InvoiceContactEmailAddress { get; set; }
    public List<Item>? Items { get; set; }
}

[PrimaryKey("OrderItemId")]
public class Item
{   
    public int OrderItemId { get; set; }
    public string? ProductName { get; set; }
    public string? PurchaseOrder { get; set; }
    public string? ItemName { get; set; }
    public string? MonthName { get; set; }
    public int Year { get; set; }
    public decimal GrossPrice { get; set; }
    public decimal NetPrice { get; set; }
}

My Index view with a simple form and a table to display the entered data in an EF Core in memory db

<div class="text-center">
    <h1 class="display-4">Invoice Request</h1>
    <p>We require further information.</p>

    <form method="post">

        <div class="row mb-3">
            <div class="col-md-4">
                <input type="text" class="form-control mb-2" name="OrderId" placeholder="Order Id" required="required">
                <input type="text" class="form-control mb-2" name="SalesPerson" placeholder="Sales Person">
                <input type="text" class="form-control mb-2" name="OrderConfirmedDate" placeholder="Order Confirmed Date">
                <input type="text" class="form-control mb-2" name="CurrencyName" placeholder="Currency Name">
                <input type="text" class="form-control mb-2" name="SpecialInstructions" placeholder="Special Instructions">
                <input type="text" class="form-control mb-2" name="InvoiceAdvertiser" placeholder="Invoice Advertiser">
                <input type="text" class="form-control mb-2" name="InvoiceCompanyName" placeholder="Invoice Company Name">
            </div>

            <div class="col-md-4">
                <input type="text" class="form-control mb-2" name="InvoiceAddress1" placeholder="Invoice Address 1">
                <input type="text" class="form-control mb-2" name="InvoiceAddress2" placeholder="Invoice Address 2">
                <input type="text" class="form-control mb-2" name="InvoiceAddress3" placeholder="Invoice Address 3">
                <input type="text" class="form-control mb-2" name="InvoiceCity" placeholder="Invoice City">
                <input type="text" class="form-control mb-2" name="InvoiceStateCounty" placeholder="Invoice State County">
                <input type="text" class="form-control mb-2" name="InvoicePostCode" placeholder="Invoice Post Code">
                <input type="text" class="form-control mb-2" name="InvoiceCountryName" placeholder="Invoice Country Name">
            </div>

            <div class="col-md-4">
                <input type="text" class="form-control mb-2" name="InvoiceContactName" placeholder="Invoice Contact Name">
                <input type="email" class="form-control mb-2" name="InvoiceContactEmailAddress" placeholder="Invoice Contact Email Address">
            </div>
        </div>

        <div class="row mb-3">
            <div class="col-md-12 mb-3">
                <h4>Add/Remove Item to Request</h4>
                <button class="btn btn-secondary" type="button">-</button>
                <button class="btn btn-secondary" type="button">+</button>
            </div>
            <div class="col-md-6">
                <input type="text" class="form-control mb-2" name="Items[0].OrderItemId" placeholder="Order Item Id" required="required">
                <input type="text" class="form-control mb-2" name="Items[0].ProductName" placeholder="Product Name">
                <input type="text" class="form-control mb-2" name="Items[0].PurchaseOrder" placeholder="Purchase Order">
                <input type="text" class="form-control mb-2" name="Items[0].ItemName" placeholder="Item Name">
            </div>

            <div class="col-md-6">
                <input type="text" class="form-control mb-2" name="Items[0].MonthName" placeholder="Month Name, e.g. January">
                <input type="text" class="form-control mb-2" name="Items[0].Year" placeholder="Year">
                <input type="text" class="form-control mb-2" name="Items[0].GrossPrice" placeholder="Gross Price">
                <input type="text" class="form-control mb-2" name="Items[0].NetPrice" placeholder="Net Price">
            </div>
        </div>

        <div class="row">
            <div class="col">
                <button type="submit" class="btn btn-primary">Add Request</button>
            </div>
        </div>
    </form>

    <div class="mt-3">
        <table class="table">
            <thead>

            <tr>
                <th>OrderId</th>
                <th>SalesPerson</th>
                <th>OrderConfirmedDate</th>
                <th>CurrencyName</th>
                <th>SpecialInstructions</th>
                <th>InvoiceAdvertiser</th>
                <th>InvoiceCompanyName</th>
                <th>InvoiceAddress1</th>
                <th>InvoiceAddress2</th>
                <th>InvoiceAddress3</th>
                <th>InvoiceCity</th>
                <th>InvoiceStateCounty</th>
                <th>InvoicePostCode</th>
                <th>InvoiceCountryName</th>
                <th>InvoiceContactName</th>
                <th>InvoiceContactEmailAddress</th>
                <th>Items</th>
            </tr>
            </thead>

            <tbody>
            @foreach (var request in Model.RequestsList)
            {
                <tr>
                    <td>@request.OrderId</td>
                    <td>@request.SalesPerson</td>
                    <td>@request.OrderConfirmedDate</td>
                    <td>@request.CurrencyName</td>
                    <td>@request.SpecialInstructions</td>
                    <td>@request.InvoiceAdvertiser</td>
                    <td>@request.InvoiceCompanyName</td>
                    <td>@request.InvoiceAddress1</td>
                    <td>@request.InvoiceAddress2</td>
                    <td>@request.InvoiceAddress3</td>
                    <td>@request.InvoiceCity</td>
                    <td>@request.InvoiceStateCounty</td>
                    <td>@request.InvoicePostCode</td>
                    <td>@request.InvoiceCountryName</td>
                    <td>@request.InvoiceContactName</td>
                    <td>@request.InvoiceContactEmailAddress</td>
                    <td>
                        @if (@request.Items != null)
                        {
                            @foreach (var item in @request.Items)
                            {
                                <p>@item.OrderItemId</p>
                            }
                        }
                    </td>

                </tr>
            }
            </tbody>
        </table>
    </div>
</div> 

This is my Index.cshtml.cs file that binds the data:

public class IndexModel : PageModel
{
    private readonly RequestDbContext _context;

    public List<Request> RequestsList { get; set; } = [];
    
    [BindProperty] 
    public Request? NewRequest { get; set; }
    
    public IndexModel(RequestDbContext context)
    {
        _context = context;
    }

    public void OnGet()
    {
        RequestsList = _context.Requests.ToList();
    }

    public IActionResult OnPost()
    {
        _context.Requests.Add(NewRequest);
        _context.SaveChanges();
        
        return RedirectToPage();
    }
}

Any help much appreciated