Veritabanından Tek Bir Değer Okuma C#

string connectionString1 = ConfigurationManager.ConnectionStrings["caglayanCS"].ConnectionString;
SqlConnection baglanti = new SqlConnection(connectionString1);

        SqlCommand sorgu = new SqlCommand("Select kullaniciadi from yorumTablosu where yorumid=" + e.CommandArgument.ToString() + "", baglanti);
        baglanti.Open();
        string yorumcuadi = sorgu.ExecuteScalar().ToString();
        baglanti.Close();