Question

I only use DataReaders two times within my application both times it looks like this

    MySqlDataReader reader = cmd.ExecuteReader();
    while (reader.Read())
    {
       //Code
    }
    reader.Close();

Can anyone give me some pointers on how to solve this error? Or where to look? Sorry if it’s too vague but that’s what the error is telling me. It points to this point:

        MySqlCommand cmdDel = new MySqlCommand("UPDATE " + _Database + " SET balance=" + balance + ", bitaddress=" + myads + ", lostbalance=" + lostbalance + " WHERE username = '" + username + "'", connection);
        cmdDel.ExecuteNonQuery();
        cmdDel.Dispose();

My guess is that executing query commands could be not allowed inside of a while(reader.Read()) can anyone confirm on this?

Answer 1

This almost certainly implies that you’re sharing a connection object between multiple command objects. You should avoid doing this (unless they’re all involved in a single database transaction).

The model you should follow generally is:

using(var connection = new MySqlConnection("..."))
{
   using(var cmd = new MySqlCommand("...",connection))
   {
       //Set up parameters/other settings/as required
       connection.Open();
       cmd.<Whatever ExecuteXXX method you need to use>();
       //If it was ExecuteReader, process the results now
   }
}
//If it was ExecuteScalar, or a fill of a DataSet or DataTable, consume the results now

Unless you have specific needs which prevent it, you should prefer to wrap disposables in using statements, rather than manually calling Dispose().