private void button1_Click(object sender, EventArgs e)
 {
     this.Close();
     MenuPrincipal m = new MenuPrincipal();
     m.Show();
 }
 private void salirToolStripMenuItem_Click(object sender, EventArgs e)
 {
     this.Close();
     MenuPrincipal m = new MenuPrincipal();
     m.Show();
 }