//abrir ventana tarifas
private void tarifasToolStripMenuItem_Click(object sender, EventArgs e)
{
if (tarifas == null)
{
tarifas = new Tarifas();
tarifas.MdiParent = this;
tarifas.FormClosed += new FormClosedEventHandler(CerrarFormaTarifas);
tarifas.Show();
}
else
{
tarifas.Activate();
}
}
private void CerrarFormaTarifas(object sender, FormClosedEventArgs e)
{
tarifas = null;
}