Saving data from SQLDataReader to FileStream with minimal memory usage

I've wrapped a SQLDataReader as an IEnumberable using a yield statement. I'd like use this to dump to a file. I'm seeing some pretty heavy memory utilization. Was wondering if anyone had any ideas on how to do this with minimal or set memory utilization. I don't mind specifying a buffer I'd just like to know what it'll be before I unleash this on an unsuspecting server.

I've been using something like the following:

class Program
{
    static void Main(string[] args)
    {

        var fs = File.Create("c:\\somefile.txt");
        var sw = new StreamWriter(fs);


        foreach (var asdf in Enumerable.Range(0, 500000000))
        {
            sw.WriteLine("adsfadsf");//Data from Reader

        }
        sw.Close();

    }
}

        string commandText = @"SELECT name FROM {0} WHERE name NOT LIKE '%@%'";

        SqlCommand sqlCommand = new SqlCommand(string.Format(commandText, list.TableName.SQLEncapsulate()),
                                               _connection);

        using (SqlDataReader sqlDataReader = sqlCommand.ExecuteReader())
        {
            while (sqlDataReader.Read())
            {
                yield return sqlDataReader["name"].ToString();
            }
        }