Set isolation w/o an ifxtransaction?

I'm trying to execute a simple select query using IfxCommand. I would like to set isolation to dirty read, but I have only found examples of setting isolation level in the context of an IfxTransaction. I do not require a transaction as I am only issuing a select statement. Below is my current code, is this the best approach? Also, if y开发者_JAVA百科ou know how long the isolation level stays set to dirty read I would like to know.

DataSet ds = new DataSet();
        IfxConnection connection = new IfxConnection(ConfigurationManager.ConnectionStrings[connectionStringName].ConnectionString);
        IfxCommand command = new IfxCommand();

        try
        {
            connection.Open();                
            command.Connection = connection;
            command.CommandText = "SET ISOLATION TO DIRTY READ";
            command.ExecuteNonQuery();

            command.CommandText = BuildCommandString();

            IfxDataAdapter idap = new IfxDataAdapter(command.CommandText, connection);
            idap.Fill(ds);
        }

Would

using (var noTransaction = new TransactionScope(TransactionScopeOption.Suppress)) {
  // Use your connection here
}

work? Not sure if Informix enlists itself in ambient transactions? Or - if you want to set the isolationlevel explicitly in a nested transaction:

var txOptions = new TransactionOptions();
txOptions.IsolationLevel = IsolationLevel.ReadUncommitted;
txOptions.Timeout.TotalSeconds * 2));
using (var noTransaction = new TransactionScope(TransactionScopeOption.RequiresNew, txOptions)) {
  // Use your connection here
}

Edit: Just read the comment that refered to Informix and TransactionScopes. You'd have to change the code to reflect the solution there.