Getting RFID tag data using C#

Question

I am trying to get an RFID tag number using a WinForms application. But whenever I click the Button the application stops responding. Please help regarding this.

Arduino code

void setup() {
  Serial.begin(9600);
  SPI.begin();
  rfid.init();
}

void loop() {
  if(rfid.isCard()) {
    if(rfid.readCardSerial()) {
      Serial.print(rfid.serNum[0], HEX);
      Serial.print(" ");
      Serial.print(rfid.serNum[1], HEX);
      Serial.print(" ");
      Serial.print(rfid.serNum[2], HEX);
      Serial.print(" ");
      Serial.print(rfid.serNum[3], HEX);
      Serial.print(" ");
      Serial.print(rfid.serNum[4], HEX);
      Serial.println("");
      delay(1000);
    }
  }
  rfid.halt();
}

C# code

private void button1_Click(object sender, EventArgs e) {
  try {
    serialPort1.Open();
    serialPort1.DataReceived += new SerialDataReceivedEventHandler(serialPort1_DataReceived);
    textBox2.Text = "connected";
    serialPort1.Close();
  }
  catch(Exception ex) {
    textBox2.Text = "Com port disconnected";
  }
}

private void serialPort1_DataReceived(object sender, SerialDataReceivedEventArgs e) {
  SerialPort sp = (SerialPort)sender;
  string indata = sp.ReadExisting();
  textBox1.Text = indata;
}

Answer 1

You are closing the port immediately after you open it. You need to keep it open while you are expecting data. Remove the line

serialPort1.Close();

Then, in the callback you try to access the GUI from the callback thread. That's not allowed. Use Invoke().

private void serialPort1_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
     SerialPort sp = (SerialPort)sender;
     //string indata = sp.ReadExisting();
     string indata = sp.ReadLine();
     //textBox1.Text = indata;
     Invoke(new Action<string>(
         (s) => 
         {
             textBox1.Text = s;
         }
     ), indata);
}