Arduino to C# Data Receive

Question

I've asked this question earlier today, but have refined my code so am putting a new question up here.

This is the code I have at the moment:

Arduino Code:

void setup()
{
 pinMode(13,OUTPUT);
 digitalWrite(13,LOW);

 Serial.begin(9600);
}

void loop()
{
 if(Serial.available() > 0)
 {
  char letter = Serial.read();

  if (letter == 'A')
  {
   digitalWrite(13,HIGH);
   Serial.println("THE LED IS ON");
  }
  else if (letter == 'B')
  {
   digitalWriter(13,LOW);
   Serial.println("THE LED IS OFF");
  }
 }
}

I have a C# program with an onButton, offButton, and textboxInterface. This is the code I have in C#.

C# Code:

using System.IO.Ports;

public partial class Form1: Form
{
 public static System.IO.Ports.SerialPort serialPort1;
 private delegate void LineReceivedEvent(string line);

 public Form1()
 {
    InitizlizeComponent();
    System.ComponentModel.IContainer components = new System.ComponentModel.Container();
    serialPort1 = new System.IO.Ports.SerialPort(components);
    serialPort1.PortName = "COM7";
    serialPort1.BaudRate = 9600;
    serialPort1.DtrEnable = true;
    serialPort1.Open();
    serialPort1.DataReceived += new SerialDataReceivedEventHandler(serialPort1_DataReceived);
 }

 private static void serialPort1_DataReceived(object sender, SerialDataEventReceivedEventArgs e)
 {
    SerialPort sp = (SerialPort)sender;
    string indata = sp.ReadExisting();
    textboxInterface.Text = indata;
 }

I think that is mostly right (?), the only error I am getting is as the last textboxInterface with an error coming up saying: *An object reference is required for the non-static field, method, or property 'Arduino_Interface.Form1.textboxInterface'*

Can someone please show me what stupid thing I'm doing...

Answer 1

First, remove static from the declaration of serialPort1_DataReceived . You need access to the form's instance fields so it cannot be static .

Second, this event will be raised on a background thread and you cannot update the UI from that thread. You will need to marshal the call to UI thread to update the textbox. Something like this:

private void serialPort1_DataReceived(object sender, SerialDataEventReceivedEventArgs e)
{
    SerialPort sp = (SerialPort)sender;
    string indata = sp.ReadExisting();
    this.BeginInvoke(new Action(() => textboxInterface.Text = indata));
}