c# MySQL连接池限制，并清理连接

我有一个简单的DB管理器类(一个比它的能力更大的名字):

class DbManager
{
    private MySqlConnectionStringBuilder _connectionString;
    public DbManager()
    {
        _connectionString = new MySqlConnectionStringBuilder();
        _connectionString.UserID = Properties.Database.Default.Username;
        _connectionString.Password = Properties.Database.Default.Password;
        _connectionString.Server = Properties.Database.Default.Server;
        _connectionString.Database = Properties.Database.Default.Schema;
        _connectionString.MaximumPoolSize = 5;
    }

    public MySqlConnection GetConnection()
    {
        MySqlConnection con = new MySqlConnection(_connectionString.GetConnectionString(true));
        con.Open();
        return con;
    }
}

然后我在其他地方有另一个类，表示其中一个表中的记录，我像这样填充它:

class Contact
{
    private void Populate(object contactID)
    {
        using (OleDbConnection con = DbManager.GetConnection())
        {
            string q = "SELECT FirstName, LastName FROM Contacts WHERE ContactID = ?";
            using (OleDbCommand cmd = new OleDbCommand(q, con))
            {
                cmd.Parameters.AddWithValue("?", contactID);
                using (OleDbDataReader reader = cmd.ExecuteReader())
                {
                    if (reader.HasRows)
                    {
                        reader.Read();
                        this.FirstName = reader.GetString(0);
                        this.LastName = reader.GetString(1);
                        this.Address = new Address();
                        this.Address.Populate(ContactID)
                    }
                }
            }
        }
    }
}

class Address
{
    private void Populate(object contactID)
    {
        using (OleDbConnection con = DbManager.GetConnection())
        {
            string q = "SELECT Address1 FROM Addresses WHERE ContactID = ?";
            using (OleDbCommand cmd = new OleDbCommand(q, con))
            {
                cmd.Parameters.AddWithValue("?", contactID);
                using (OleDbDataReader reader = cmd.ExecuteReader())
                {
                    if (reader.HasRows)
                    {
                        reader.Read();
                        this.Address1 = reader.GetString(0);
                    }
                }
            }
        }
    }
}

现在我认为所有的using语句将确保连接在完成时返回到池中，为下一次使用做好准备，但是我有一个循环，创建了数百个这些联系人并填充它们，并且似乎连接没有被释放。

连接、命令和读取器都在它们自己的using语句中。