How let a class send a signal to the main class

Question

 The question is about the serial class. One of the class's methods is void port_dataReceived(). This function is a serial event and get triggered when a byte is received over the serial port.

 

This byte must be processed in the rest of the code. Right now I can acces it with a pushbutton and that works but I need to this to work automatically.

 

The bytes can contain instructions which places text on the userinterface. For instance "Textblok.Text += received_byte;"

 

How can I let the serial class add the byte in the the textblock? 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Diagnostics;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.IO.Ports;


class Serial
{
    private SerialPort port = new SerialPort("COM3", 115200, Parity.None, 8, StopBits.One);
    String received;

    public Serial()
    {
        port.DataReceived += new SerialDataReceivedEventHandler(port_DataReceived);
        port.Open();
    }

    public void port_DataReceived(object sender, SerialDataReceivedEventArgs e)
    {
        received = port.ReadExisting();
        Debug.Write(received);
    }

    public String getReceived()
    {
        return received;
    }
}

namespace WpfApplication1
{

    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        Serial serial = new Serial();
        public MainWindow()
        {
            InitializeComponent();
        }

        private void pagedown_Click(object sender, RoutedEventArgs e)
        {
            Textblok.Text = serial.getReceived();
            Debug.Write("hello world");
        }

        private void menu_Click(object sender, RoutedEventArgs e)
        {

        }

        private void pageup_Click(object sender, RoutedEventArgs e)
        {

        }

        private void stop_Click(object sender, RoutedEventArgs e)
        {

        }

        private void step_Click(object sender, RoutedEventArgs e)
        {

        }

        private void start_Click(object sender, RoutedEventArgs e)
        {

        }
    }
}