private void Add_User(object sender, RoutedEventArgs e)
        {
            UserEditorDialog userEditor = new UserEditorDialog(ViewModel.Model);

            if (userEditor.ShowDialog() == true)
            {
                ViewModel.AddUser(userEditor.User, userEditor.NewPassword);
            }
        }
        private void Edit_User(object sender, RoutedEventArgs e)
        {
            UserEditorDialog userEditor = new UserEditorDialog(ViewModel.Model, ViewModel.SelectedUser);

            if (userEditor.ShowDialog() == true)
            {
                IUser user = userEditor.User;
                switch (userEditor.EditedField)
                {
                case UserEditorDialog.UserField.NAME:
                    ViewModel.SaveUserName(user.UserID, user.Username);
                    break;

                case UserEditorDialog.UserField.PASS:
                    ViewModel.SaveUserPass(user.UserID, userEditor.NewPassword);
                    break;

                case UserEditorDialog.UserField.TYPE:
                    ViewModel.SaveUserType(user.UserID, user.UserType);
                    break;
                }
            }
        }