Using TransactionScope

I was wondering today, while playing around, why aren’t my SQL commands, executed within a transaction rolled back, when there is an error. I found out, that in order for this to happen, connection must be opened within the transaction block. Not before. So:

connection.Open();
using(TransactionScope tx = new TransactionScope(TransactionScopeOption.Required)) {
    // executed statements here are NOT part of transaction
}
conn.Close();

instead, one must open a connection inside using block. Like so:

using(TransactionScope tx = new TransactionScope(TransactionScopeOption.Required)) {
    conn.Open();
    // execute statements
    conn.Close();
    tx.Complete(); // set complete flag in order for transaction to succeed.
}

If you don’t call TransactionScope.Complete() method, the transaction will rolback (when Dispose happens).