创建虚拟属性和静态Create()方法的意义

public class Product
{
    private decimal _price;
    public string Name { get; set; }

    public decimal Price
    {
        get { return _price; }
        set
        {
            if (value < 0)
                throw new ArgumentException("Price cannot be negative");
            _price = value;
        }
    }

    public decimal TotalPrice
    {
        get { return Price * Quantity; }
    }

    public int Quantity { get; set; }
}

public class User
{
    private string _username;
    private string _email;

    private User(string username, string email)
    {
        _username = username;
        _email = email;
    }

    public static User Create(string username, string email)
    {
        if (string.IsNullOrEmpty(username))
            throw new ArgumentException("Username cannot be null or empty");
        if (string.IsNullOrEmpty(email))
            throw new ArgumentException("Email cannot be null or empty");

        return new User(username, email);
    }

    public string Username => _username;
    public string Email => _email;
}