An item with the same key has already been added.

_uow.Update(employee, x => x.OwnedCollection(y => y.RemainingLessons));

public User SelectedUser { get; set; }

private void doDelete()
{
    _sendMsg.ShowMsg(new AlertConfirmBoxModel
    {
        Errors = new List<string> { "آیا کاربر انتخاب شده حذف شود؟" },
        ShowConfirm = Visibility.Visible,
        ShowCancel = Visibility.Visible
    },
    confirmed: input => delete(input));
}

private void delete(AlertConfirmBoxModel input)
{
    UsersList.Remove(SelectedItem);
}