private void inventorylogBttn_Click(object sender, EventArgs e)
{
if (inventorylogform == null)
{
inventorylogform = new inventorylogFrm();
inventorylogform.FormClosed += inventorylogform_FormClosed;
}
inventorylogform.Show(this);
Hide();
}
void inventorylogform_FormClosed(object sender, FormClosedEventArgs e)
{
inventorylogform = null;
Show();
}