how to read fields from a data reader

Hello experts,
Can anyone tell me what I'm doing wrong with this data reader? I'm getting a result back when I query the database directly. Browser error is Invalid attempt to read when no data is present.

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack) 
        {
            Session["uid"] = Request.QueryString["uid"];

            SqlCommand command;
            SqlConnection conn;
            SqlDataReader dr = null;

            string sqlString = @" SELECT first_name + ' ' + last_name full_name FROM people WHERE network_account = @network_account";

            using (conn = new SqlConnection(ConfigurationManager.ConnectionStrings["AdHocReportingConnectionString"].ConnectionString.ToString()))
            {
                using (command = conn.CreateCommand())
                {
                    conn.Open();
                    command.CommandText = sqlString;
                    command.CommandType = CommandType.Text;
                    command.Parameters.AddWithValue("@network_account", Session["uid"].ToString());

                    using (dr = command.ExecuteReader(CommandBehavior.SingleResult))
                    {
                        if (dr.HasRows)
                        {
                            Session["FullName"] = dr["full_name"].ToString();
                        }
                    }
                }
            }
        }

        this.Label1.Text = Session["FullName"].ToString();
     }

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