ALGA/ALGA/Product.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Runtime.CompilerServices;

namespace OE.ALGA;

public class Product
{
    [Validation(AttributeValidation.NotEmpty)]
    public string Name { get; }
    
    [Validation(AttributeValidation.PositiveNumber)]
    public decimal Price { get; }

    [Validation(AttributeValidation.NonNegative)]
    public int Quantity { get; }

    [Validation(AttributeValidation.FutureDate)]
    public DateTime? Experiation { get; }

    public Product(string name, decimal price, int quantity, DateTime? experiarion)
    {
        Name = name;
        Price = price;
        Quantity = quantity;
        Experiation = experiarion;
    }
}
public enum AttributeValidation
{
    NotEmpty,
    PositiveNumber,
    NonNegative,
    FutureDate
}
public class ValidationAttribute : Attribute
{
    public AttributeValidation Rule { get; }
    public ValidationAttribute(AttributeValidation rule)
    {
        Rule = rule;
    }
}
public static class Validator
{
    public static void Validate(Product product)
    {
        bool flag = false;
        var t = product.GetType();

        foreach (var p in t.GetProperties())
        {
             var value = p.GetValue(product);

            switch (p.GetCustomAttribute<ValidationAttribute>().Rule)
            {
                case AttributeValidation.NotEmpty:
                    if (Convert.ToString(value) == "")
                    {
                        flag = true;
                    }
                    break;

                case AttributeValidation.PositiveNumber:
                    if (Convert.ToInt32(value) <= 0)
                    {
                        flag = true;
                    }
                    break;

                case AttributeValidation.NonNegative:
                    if (Convert.ToInt32(value) < 0)
                    {
                        flag = true;
                    }
                    break;

                case AttributeValidation.FutureDate:
                    if (Convert.ToDateTime(value) < DateTime.Now)
                    {
                        flag = true;
                    }
                    break;
            }
            
        }
        if (flag)
        {
            throw new WrongProductException();
        }
        else
        {
            Console.WriteLine("Product added successfuly");
        }
    }
}
public class WrongProductException : Exception
{

}