Slice/Cashier/Helper.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;

namespace Cashier
{
    public class Helper
    {
        public static void ErrorMessage(string message)
        {
            MessageBox.Show(message, "Ошибка", MessageBoxButton.OK, MessageBoxImage.Error);
        }
        public static void InformationMessage(string message)
        {
            MessageBox.Show(message, "Ошибка", MessageBoxButton.OK, MessageBoxImage.Information);
        }
    }
}