private void listarClienteToolStripMenuItem_Click(object sender, EventArgs e)
{
if (telaListarCliente == null)
{
telaListarCliente = new Listar_Cliente();
telaListarCliente.Show();
telaListarCliente.MdiParent = this;
telaListarCliente.Disposed += new EventHandler(telaListarCliente_Disposed);
}
}
void telaListarCliente_Disposed(object sender, EventArgs e)
{
telaListarCliente = null;
}