Problem With Update GridView

protected void GrdViewCont_RowUpdating(object sender, GridViewUpdateEventArgs e)
        {
            Label Lblid = (Label)GrdViewCont.Rows[e.RowIndex].FindControl("LblNo");
            TextBox txtNam = (TextBox)GrdViewCont.Rows[e.RowIndex].FindControl("txtName");
            Label Lbltp = (Label)GrdViewCont.Rows[e.RowIndex].FindControl("LblType");

            SqlCommand cmd = new SqlCommand("update ContarctorDefTable set Contractor_Name = '" + txtNam.Text + "'" +
                            ",Contractor_Type='" + LblType.Text + "' where ID = '" + Lblid.Text + "'", conn);
            conn.Open();
            SqlDataReader reader;
            reader = cmd.ExecuteReader();
            conn.Close();
        
            GrdViewCont.EditIndex = -1;
            BindGrdViewCont();
        }