ModelState showing validationstate as invalid for a field that is not required

Question

I am using Razor Pages. I have two fields that in a model that are NOT required:

`    public class OrderModel : EntityModel, IValidatableObject
    {        
        public string UserId { get; set; } 
        public int PortfolioId { get; set; }
        public int StockId { get; set; }
        public int StockHoldingId { get; set; }
        public string StockSymbol { get; set; } 

        [Required]
        [DisplayName("Shares Traded")]
        public int QuantityTraded { get; set; }`

The two fields are UserId and StockSymbol. I have the following portion of a form, with the UserId and StockSymbol being nonexistent so null or empty, which I am purposely doing:

`        <div>
            Quantity: <input type="number" min="0" asp-for="@Model.Order.QuantityTraded" />
            <input type="hidden" asp-for="@Model.Stock.Id" />
            <input type="hidden" asp-for="@Model.Stock.Symbol" />
            <input type="hidden" asp-for="@Model.Stock.Price" />
            <input type="hidden" asp-for="@Model.Stock.StockName" />
            <input type="hidden" asp-for="@Model.Stock.Description" />
            <input class="btn-primary" type="submit" value="Buy" asp-page-handler="Buy" />
            <input class="btn-primary" type="submit" value="Sell" asp-page-handler="Sell" />
        </div>`

When I submit the form, I am having an invalid ModelState as shown below:

It is showing "UserId field is required" and "StockSymbol field is required". What else can be causing this requirement, when the [Required] attribute is clearly not there for them?

As requested, Here is the Validate method:

public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
{
    if (QuantityTraded < 1)
    {
        yield return new ValidationResult(
            $"Quantity must be greater than 0.",
            new[] { nameof(QuantityTraded) });
    }
}

Answer 1

Do this. may be following things will help you. Its applicable for updated .NET core 5 > versions.

public class OrderModel
{        
    public string? UserId { get; set; }
    public string? StockSymbol { get; set; }
}

Or remove following tag in .csproj file

<Nullable>enable</Nullable>