public void ShowDialog()
        {
            if (AssignableUsers.Any())
            {
                Users.Clear();
                foreach (User u in AssignableUsers.OrderByDescending(u => u.IsMechanic))
                {
                    Users.Add(new Tuple <int, string, bool>(u.UserId, u.FullName, AssignedUsers.Where(us => us.UserId == u.UserId).Any()));
                }
                FrmOptionPicker = new frmOptionPicker(ParentForm, Users);
                DialogResult result = FrmOptionPicker.ShowDialog(ParentForm);
                if (result == DialogResult.OK)
                {
                    var PickedItems = FrmOptionPicker.ReturnItems;
                    AssignedUsers.Clear();

                    if (PickedItems.Any(i => i.Item3 == true))
                    {
                        foreach (var item in PickedItems.Where(i => i.Item3 == true))
                        {
                            AssignedUsers.Add(new User {
                                UserId = item.Item1, Name = item.Item2
                            });
                        }
                        AssignedUserNames = "Przypisani: " + string.Join(", ", PickedItems.Where(t => t.Item3).Select(t => t.Item2).ToList());
                    }
                    else
                    {
                        AssignedUserNames = "Przypisani: ";
                    }
                }
            }
        }