store queryresult to a string

I am trying to read the query result into a string, Any ideas
 protected void Page_Load(object sender, EventArgs e)     {         NameValueCollection coll = HttpContext.Current.Request.Headers;         string username = coll["SMUSER"];         SqlConnection myConn = new SqlConnection(ConfigurationManager.ConnectionStrings["conn"].ToString());         string strSQL = "select Role from Role where UserID LIKE '"+username+"' ";         DataTable dt = new DataTable();         DataSet ds = new DataSet();         ds.Clear();         string role = ds.Tables[0].Rows[0];
    ...