private void btncrear_Click(object sender, EventArgs e)
{
BaseDeDatos.CrearTabla(txtcreartabla.Text, lb.Items.OfType <string>().ToArray());
actualizar(0);
}
string id_nuevo()
{
var ids = new BaseDeDatos("Usuarios").Abrir().Select(x => x[0]).ToList();
return(ids.Count == 1 ? "0" : (int.Parse(ids[ids.Count - 1]) + 1).ToString());
}