private void nhàCungCấpToolStripMenuItem_Click(object sender, EventArgs e)
 {
     NhaCungCap NCC = new NhaCungCap();
     NCC.Show();
 }
 private void button1_Click(object sender, EventArgs e)
 {
     NhaCungCap NCC = new NhaCungCap();
     NCC.ShowDialog();
 }