ASP.Net SqlDataReader Error: Invalid attempt to read when no data is present

How to remove error Invalid attempt to read when no data is present

protected void btn_check_Click(object sender, EventArgs e)
{
    string constr = ConfigurationManager.ConnectionStrings["IntranetConnectionString"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT Mtrl_cd,dsc,qunty FROM Mtrl_rcpt_rgster_cni_lab WHERE Mtrl_cd = '" + txt_Mtrl_cd1.Text + "'"))
        {
            cmd.CommandType = CommandType.Text;
            cmd.Connection = con;
            con.Open();
            using (SqlDataReader sdr = cmd.ExecuteReader())
            {
                sdr.Read();
                txt_Mtrl_cd.Text = sdr["Mtrl_cd"].ToString();
                txt_dsc.Text = sdr["Mtrl_dscrptn"].ToString();
                Labelttl1.Text = sdr["quntty_req"].ToString();
            }
 
            con.Close();
        }
    }
}