C# MySqlDataReader in MySqlDataReader

Asked Mar 20 '16 at 23:36

Active Mar 20 '16 at 23:36

Viewed 333 times

In php I have something like that:

$zapytanie1 = "SELECT * FROM tabelka2";
$wykonaj1 = mysql_query($zapytanie1);
while($dane1 = mysql_fetch_array($wykonaj1))
{
$idzs = $dane1['id'];
$zapytanie2 = "SELECT * FROM tabelka2 WHERE dane=$idzs";
$wykonaj = mysql_query($zapytanie2);
while($dane2 = mysql_fetch_array($wykonaj2))
{
$nazwa = $dane2['name'];
}
echo $nazwa;
}

If I make something like that in C#:

    MySqlCommand zapytanieW = new MySqlCommand("SELECT * from tabelka1", Polaczenie);
            MySqlDataReader drW = zapytanieW.ExecuteReader();
            while (drW.Read())
            {
                double id = Convert.ToDouble(drW["id"]);
   MySqlCommand zapytanieWZ = new MySqlCommand("SELECT * from tabelka2 WHERE dane="+id+"", Polaczenie);
            MySqlDataReader drWZ = zapytanieWZ.ExecuteReader();
            while (drWZ.Read())
            {
                string nazwa = Convert.ToString(drW["nazwa"]);
}}

I get error: There is already an open DataReader associated with this Connection which must be closed first

But I cant closed first one. How can I do somthing like in PHP example?

asked Mar 20 '16 at 23:36

harbii

1

You need to read all rows of your first data reader before start an other. Or merge the two query in one with a `join` – Kalten Mar 20 '16 at 23:42
I can't use join. Any other suggestions? – harbii Mar 20 '16 at 23:51
And with an old school where clause ? `select * from T1, T2 where T1.T1_Id = T2.T1_Id`. You can also store store ids of first table into a list. – Kalten Mar 20 '16 at 23:53
Old school. How it should be according to the new school? – harbii Mar 22 '16 at 23:11

C# MySqlDataReader in MySqlDataReader

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