private void dangXuatToolStripMenuItem_Click(object sender, EventArgs e)
{
if (!kiemtratontai("frmlogin"))
{
frmlogin f = new frmlogin();
hienthimpi(f);
}
}
private void FrmMain_Load(object sender, EventArgs e)
{
frmlogin f = new frmlogin();
hienthimpi(f);
}