new_demo/NewOrderWindow.axaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using Avalonia.Controls;
using Avalonia.Interactivity;
using demo_hard.Models;

namespace demo_hard;

public partial class NewOrderWindow : Window
{

    public NewOrderWindow()
    {
        InitializeComponent();
    }
    public NewOrderWindow(Client client, List<Service> selectedServices, int duration )
    {
        InitializeComponent();
        using var context = new User2Context();
        List<int> orderNumbers = new List<int>();
        orderNumbers = new List<int>(context.Orders.Select(o=>o.Id));
        
        OrderNumberText.Text = orderNumbers.Count+1.ToString();
        ClientCode.Text = client.ClientCode.ToString();
        TimeOrder.Text = DateTime.Now.ToString("dd/MM/yyyy HH:mm:ss");
        FIO.Text = client.Fio;
        Address.Text = client.Address;
        ServicesList.ItemsSource = selectedServices.Select(it => it.ServiceName).ToList();
        var totalcost = selectedServices.Sum(it =>
        {
            var serviceCost = decimal.TryParse(it.ServiceCost, out var cost) ? cost : 0;
            return cost;
        });
        Cost.Text = $"{totalcost}.00 руб.";
    }

    private void ButtonBack_OnClick(object? sender, RoutedEventArgs e)
    {
        new OrderWindow().ShowDialog(this);
    }
}