private void Update()
        {
            ComboBoxIndexContent selected = cmbProduct.SelectedItem as ComboBoxIndexContent;

            if (selected != null)
            {
                tbProduct.Text = selected.Content;
            }
            else
            {
                tbProduct.Text = string.Empty;
            }
        }
        private bool IsNotOwner(List <OwnersMagazijn> owners, ComboBoxIndexContent item)
        {
            int count = 0;

            for (int i = 0; i < owners.Count(); i++)
            {
                if (owners[i].UserId == item.Id)
                {
                    count++;
                }
            }
            if (count != 0)
            {
                return(true);
            }
            else
            {
                return(false);
            }
        }