private void button3_Click_1(object sender, EventArgs e)
        {
            QuanLiThongTinNhanVien_GUI x = new QuanLiThongTinNhanVien_GUI();

            this.Hide();
            x.ShowDialog();
        }
        private void themTKToolStripMenuItem_Click(object sender, EventArgs e)
        {
            QuanLiThongTinNhanVien_GUI x = new QuanLiThongTinNhanVien_GUI();

            this.Hide();
            x.ShowDialog();
        }