private void button1_Click(object sender, EventArgs e)
{
DanhSachKhachHang f = new DanhSachKhachHang();
f.Show();
}
private void DanhSachKhachHangToolStripMenuItem_Click(object sender, EventArgs e)
{
DanhSachKhachHang frmDanhSạhKhachHang = new DanhSachKhachHang();
frmDanhSạhKhachHang.Show();
}