Product.cs

public class Product : MyEntity
{
    [Required]
    [StringLength(ProductInvariants.NameMaxLength)]
    public string Name { get; private set; }

    [Required]
    [StringLength(ProductInvariants.DescriptionMaxLength)]
    public string Description { get; private set; }

    [Required]
    public Money Price { get; private set; }

    [Required]
    public Mass Mass { get; private set; }

    public int NumberInStock { get; private set; }

    // EF
    private Product()
    {
        Name = null!;
        Description = null!;
        Mass = null!;
        Price = null!;
    }

    public Product(string name, string description, Money price, Mass mass)
    {
        UpdateName(name);
        UpdateDescription(description);

        CheckMass(mass?.Value ?? throw new ArgumentNullException(nameof(mass)));
        CheckPrice(price?.Amount ?? throw new ArgumentNullException(nameof(price)));

        Mass = mass;
        Price = price;

        NumberInStock = 0;
    }

    public void UpdateMass(float value)
    {
        CheckMass(value);
        Mass = new Mass(value, Mass?.Unit ?? ProductInvariants.DefaultMassUnit);
    }

    public void UpdatePrice(decimal amount)
    {
        CheckPrice(amount);
        Price = new Money(amount, Price?.Currency ?? ProductInvariants.DefaultPriceCurrency);
    }

    [MemberNotNull(nameof(Name))]
    public void UpdateName(string value)
    {
        if (string.IsNullOrWhiteSpace(value))
            throw new ArgumentException("Name cannot be empty.");

        if (value.Length > ProductInvariants.NameMaxLength)
            throw new ArgumentException($"Length of value ({value.Length}) exceeds maximum name length ({ProductInvariants.NameMaxLength}).");

        Name = value;
    }

    [MemberNotNull(nameof(Description))]
    public void UpdateDescription(string value)
    {
        if (string.IsNullOrWhiteSpace(value))
            throw new ArgumentException("Description cannot be empty.");

        if (value.Length > ProductInvariants.DescriptionMaxLength)
            throw new ArgumentException($"Length of value ({value.Length}) exceeds maximum description length ({ProductInvariants.NameMaxLength}).");

        Description = value;
    }

    /// <summary>
    /// Adjust product stock based on a transaction occurred.
    /// </summary>
    internal void RecordTransaction(TransactionLine transactionLine)
    {
        if (transactionLine.Quantity < 1)
            throw new ArgumentException("Product quantity in transaction must be 1 or greater.");

        switch (transactionLine.Transaction.TransactionType)
        {
            case TransactionType.Sales:
                if (transactionLine.Quantity > NumberInStock)
                    throw new InsufficientStockException(this, transactionLine.Quantity, NumberInStock);
                NumberInStock -= transactionLine.Quantity;
                break;
            case TransactionType.Procurement:
                NumberInStock += transactionLine.Quantity;
                break;
            default:
                throw new InvalidEnumArgumentException($"Unexpected {nameof(TransactionType)}: '{transactionLine.Transaction.TransactionType}'.");
        }
    }

    private static void CheckMass(float value)
    {
        if (value < ProductInvariants.MassMinimum)
            throw new ArgumentException($"Value '{value}' is smaller than the minimum required mass of {ProductInvariants.MassMinimum}.");
    }

    private static void CheckPrice(decimal amount)
    {
        if (amount < ProductInvariants.PriceMinimum)
            throw new ArgumentException($"Amount '{amount}' is smaller than the minimum required price of {ProductInvariants.MassMinimum}.");
    }
}