C# class that handle MySQL db connection
What's the point of dbConnection? As it stands now it is a barely-there wrapper around MySqlConnection with a built-in connection string(!) and some odd behavior when you call openConnection(). You claim this works, are you sure -- because why wouldn't conn.Close(); throw an exception if there isn't an open connection?



Why do you always open a transaction? Why is your connection string hard-coded?



This code:


doesn't follow capitalization standards, 
doesn't use a using statement to encapsulate classes that implement IDisposable (which should also be used when dealing with MySqlCommand and MySqlDataReader etc.), 
has bad variable names like readerSql, usernameMySql,...