private void tsPatientInvoice_Click(object sender, EventArgs e)
{
if (invoice == null)
{
invoice = new frmPatientInvoice();
invoice.MdiParent = this;
invoice.FormClosed += new FormClosedEventHandler(invoice_FormClosed);
invoice.Show();
}
else
{
invoice.Activate();
invoice.WindowState = FormWindowState.Normal;
}
}
void invoice_FormClosed(object sender, FormClosedEventArgs e)
{
invoice = null;
}