Using MySQLConnection in C# does not close properly

I try to write a class to make MySql Connections easier. My problem is, after I open a connection and close it. It is still open in the Database and gets aborted.

I'm using the 'using' statement' of course, but the connection is still open and gets aborted after I exit the program.

Here's what my code looks like:

using (DatabaseManager db = new DatabaseManager())
{
using (MySqlDataReader result = db.DataReader("SELECT * FROM module WHERE Active=1 ORDER BY Sequence ASC"))
{
    foreach (MySqlDataReader result in db.DataReader("SELECT * FROM module WHERE Active=1 ORDER BY Sequence ASC"))
    {
        //Do stuff here
    }
}
}

The class Database manager opens the connection and closes it when disposed:

public DatabaseManager()
{
    this.connectionString = new MySqlConnectionStringBuilder("Server=localhost;Database=businessplan;Uid=root;");
    connect();
}
private bool connect()
{
    bool returnValue = true;
    connection = new MySqlConnection(connectionString.GetConnectionString(false));
    connection.Open();
}

public void Dispose()
{
    Dispose(true);
}

public void Dispose(bool disposing)
{
    if (disposing)
    {
        if (connection.State == System.Data.ConnectionState.Open)
        {
            connection.Close();
            connection.Dispose();
        }
    }
    //GC.SuppressFinalize(this);//Updated
}
//Updated
//~DatabaseManager()
//{
//  Dispose(false);
//}

So, I checked it in the debugger and the Dispose()-method is called and executes correctly. What am I missing? Is there something I did wrong or misunderstood?

Just in case, the DataReader()-method (Updated version):

public IEnumerable<IDataReader> DataReader(String query)
    {
        using (MySqlCommand com = new MySqlCommand())
        {
            com.Connection = connection;
            com.CommandText = query;
            using (MySqlDataReader res