private void buttonItem2_Click(object sender, EventArgs e)
 {
     ChucVu cv = new ChucVu();
     cv.MdiParent = this;
     cv.Show();
     //this.Hide();
 }
 private void chứcVụToolStripMenuItem_Click(object sender, EventArgs e)
 {
     ChucVu cv = new ChucVu();
     cv.MdiParent = this;
     cv.Show();
 }