private void txtDien_TextChanged(object sender, EventArgs e)
{
connection = new SqlConnection(db.con);
if (txtDien.Text == String.Empty)
{
txtDien.Text = "0";
}
else
{
DataTable dt = db.getData("select Dongia from Dichvu where MaDV ='DV001'");
double tiendien = Convert.ToDouble(txtDien.Text);
double tongtien1 = 0;
foreach (DataRow dr in dt.Rows)
{
tongtien1 += double.Parse(dr["Dongia"].ToString()) * tiendien;
}
txtThanhtien1.Text = tongtien1.ToString();
}
}
private void refeshDataGridView(String sql)
{
dtgvHoadon.DataSource = db.getData(sql);
}