private void btnSua_Click(object sender, EventArgs e)
{
ECHITIETHOADON ect = new ECHITIETHOADON();
ect.SOHOADON = txtshd.Text.Trim();
ect.MASP = txtmasp.Text.Trim();
int sl = 0;
int.TryParse(txtsl.Text.Trim(), out sl);
ect.SOLUONG = sl;
float ck = 0;
float.TryParse(txtck.Text.Trim(), out ck);
ect.CHIETKHAU = ck;
BCHITIETHOADON.Update(ect);
txttongtien.Text = tongtien() + "";
}
