C# An object reference is required for the non-static field, method, or property

C# An object reference is required for the non-static field, method, or
property

I wrote a code in WPF. Firstly, i wrote a separate project to test work
with com port device and it worked well. Next i decided to integrate it in
other project but i get an error. I didn't change the code, i am just
copied it into a new code file.
This code works well:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
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;
using System.Windows.Threading;
namespace WpfApplication2
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
serial.BaudRate = 9600;
serial.Handshake = System.IO.Ports.Handshake.None;
serial.Parity = Parity.None;
serial.DataBits = 8;
serial.StopBits = StopBits.One;
serial.ReadTimeout = 200;
serial.WriteTimeout = 500;
serial.DataReceived += new
System.IO.Ports.SerialDataReceivedEventHandler(Recieve);
}
SerialPort serial = new SerialPort();
private string recieved_data;
private delegate void UpdateUiTextDelegate(string text);
private void Recieve(object sender,
System.IO.Ports.SerialDataReceivedEventArgs e)
{
if (serial.IsOpen)
{
try
{
recieved_data = serial.ReadLine();
Dispatcher.Invoke(DispatcherPriority.Send, new
UpdateUiTextDelegate(DisplayText), recieved_data);
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
}
}
private void DisplayText(string code)
{
textBox1.AppendText(string1);
}
private void button1_Click(object sender, RoutedEventArgs e)
{
ListBoxItem lbi = new ListBoxItem();
lbi = (ListBoxItem)listBox1.SelectedItem;
serial.Close();
serial.PortName = "COM" + (string)lbi.Content;
try
{
serial.Open();
textBox1.AppendText("Device opened at " + serial.PortName
+ '\n');
}
catch (Exception ex)
{
textBox1.AppendText(ex.Message + '\n');
}
}
}
}
But this one doesn't want to work and i can't understand why:
using System.IO.Ports;
using System.Windows.Threading;
using System;
using System.Windows;
namespace PresidentProtocol
{
public class QRBarCode
{
// private SerialPort serial = new SerialPort();
public QRBarCode(string com)
{
serial.BaudRate = 9600;
serial.Handshake = System.IO.Ports.Handshake.None;
serial.Parity = Parity.None;
serial.DataBits = 8;
serial.StopBits = StopBits.One;
serial.ReadTimeout = 200;
serial.WriteTimeout = 500;
serial.DataReceived += new
System.IO.Ports.SerialDataReceivedEventHandler(Recieve);
serial.Close();
serial.PortName = com;
try
{
serial.Open();
}
catch (Exception)
{
MessageBox.Show("Error opening com port.");
}
}
SerialPort serial = new SerialPort();
private string recieved_data;
private delegate void UpdateUiTextDelegate(string text);
private void Recieve(object sender,
System.IO.Ports.SerialDataReceivedEventArgs e)
{
if (serial.IsOpen)
{
try
{
recieved_data = serial.ReadLine();
Dispatcher.Invoke(DispatcherPriority.Send, new
UpdateUiTextDelegate(DisplayText), recieved_data);
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
}
}
private void DisplayText(string code)
{
MessageBox.Show(code);
}
}
}
Error: An object reference is required for the non-static field, method,
or property
'System.Windows.Threading.Dispatcher.Invoke(System.Windows.Threading.DispatcherPriority,
System.Delegate, object)'
E:\C#\PresidentProtocol\PresidentProtocol\classes\QRCodeReader.cs 48 21
PresidentProtocol
on this code:
Dispatcher.Invoke(DispatcherPriority.Send, new
UpdateUiTextDelegate(DisplayText), recieved_data);