C# display a variable in a Textbox

Question

i am sending Sensor information with a NUCLEOF411RE to my PC. I receive this data on the COM98 with a BaudRate of 115200. Now i want to program a Windows Application that will split my string and put it on my textboxes. until now i display the data with a Button_click event. It puts values on the Textboxes that actually are the real values. But if i move my Sensor and klick the button again there should be a lot more different values, but there are the same values on the textboxes. In addition i want to refresh the textboxes automatically and not with a button click.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.IO.Ports;

namespace BNO080
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            getAvailablePorts();
        }

    public string comport;
    SerialPort serial = new SerialPort();


    void getAvailablePorts()
    {
        String[] ports = SerialPort.GetPortNames();
        comboBox1.Items.AddRange(ports);
        comport = comboBox1.Text;
    } 

    private void button1_Click(object sender, EventArgs e)
    {   

        try
        {   
            if(comboBox1.Text=="" || textBox6.Text=="")
            {
                MessageBox.Show("Please Select Port Settings");
            }
            else
            {

                serial.PortName = comboBox1.Text;
                serial.BaudRate = Convert.ToInt32(textBox6.Text);
                serial.Parity = Parity.None;
                serial.StopBits = StopBits.One;
                serial.DataBits = 8;
                serial.Handshake = Handshake.None;
                serial.Open();

                MessageBox.Show("connected!");
            }
         }
        catch (UnauthorizedAccessException)
        {
            MessageBox.Show("Unauthorised Access");
        }
    }

    private void button2_Click(object sender, EventArgs e)
    {

        textBox1.Clear();
        textBox2.Clear();
        textBox3.Clear();
        textBox4.Clear();
        textBox5.Clear();
        MessageBox.Show("connection closed!");
        serial.Close();
    }

    private void button3_Click(object sender, EventArgs e)
    {
        try
        {

            textBox5.Text = serial.ReadLine();
              /*String[] Stringsizes = A.Split(new char[] {' '});
              textBox1.Text = Stringsizes[0];
              textBox2.Text = Stringsizes[1];
              textBox3.Text = Stringsizes[2];
              textBox4.Text = Stringsizes[3];*/
             // textBox5.Text = A;
            //Array.Clear(Stringsizes, 0, 3);



        }
        catch (Exception) { }
    }     
}
}

can someone help me?

As much as I hate to say these words... Application.Doevents, also make sure you use invoke, otherwise it may cross thread(the UI cannot be updated from a separate thread without an invoke). — Trey, May 24 '18 at 14:32
*"refresh the textboxes automatically"* - you can use `Timer` (there are [many](https://stackoverflow.com/q/1416803/1997232)) to call `ReadLine()`. You may want to add into question what you receive, when and what exactly you want to do with received data. — Sinatr, May 24 '18 at 14:38

score 2 · Answer 1 · answered May 24 '18 at 14:40

Can you give more information why you use the Button_Click Event to read the text? Maybe it is a possible way for you to subscribe for the DataReceived-Event of the COM-port? It would look something like this:

serial.DataReceived += new SerialDataReceivedEventHandler(DataReceivedHandler);

private static void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e)
{
    string receivedString = serial.ReadExisting();
//Do something here...
}

score 1 · Answer 2 · answered May 24 '18 at 15:43

I'd do a couple things. First subscribe to the DataReceived event on the serial port. This event handler will get called when there is data available on the serial port. Then in the event handler you can read from the serial port and add it to your textbox. You can't add it directly (see the AppendText function) because the event handler is called with a different thread, only the UI thread can update UI components (or you'll get a cross-thread exception).

...
public Form1()
{
  InitializeComponent();

  getAvailablePorts();
  // Subscribe to the DataReceived event.  Our function Serial_DataReceived
  // will be called whenever there's data available on the serial port.
  serial.DataReceived += Serial_DataReceived;
}

// Appends the given text to the given textbox in a way that is cross-thread
// safe.  This can be called by any thread, not just the UI thread.
private void AppendText(TextBox textBox, string text)
{
  // If Invoke is required, i.e. we're not running on the UI thread, then
  // we need to invoke it so that this function gets run again but on the UI
  // thread.
  if (textBox.InvokeRequired)
  {
    textBox.BeginInvoke(new Action(() => AppendText(textBox, text)));
  }
  // We're on the UI thread, we can append the new text.
  else
  {
    textBox.Text += text;
  }
}

// Gets called whenever we receive data on the serial port.
private void Serial_DataReceived(object sender,
  SerialDataReceivedEventArgs e)
{
  string serialData = serial.ReadExisting();
  AppendText(textBox5, serialData);
}

WOW thx for your help, it is working great. Is there a way you make this textBox5 variable? Now i expand the function like that. — Walter Nazarenus, May 25 '18 at 07:53

Walter Nazarenus · Answer 3 · 2018-05-29T12:37:55.607

Because i want to add an rotating 3D cube i decided to switch to WPF. I heard it is much easier to implement a 3D graphic there. So i copied my code to the new WPF project. But now i got already problems to visualize my values on the Textboxes. It doesnt work. It looks like the Evenhandler did not fire an event while receiving Data from the com port.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO.Ports;
using System.ComponentModel;
using System.Threading.Tasks;
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.Data;
using System.Drawing;


namespace cube
{
    /// <summary>
    /// Interaktionslogik für MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            getAvailablePorts();
            serial.DataReceived += Serial_DataReceived;
        }

    public bool button3clicked = false;
    public bool button4clicked = false;
    public bool button5clicked = false;
    SerialPort serial = new SerialPort();

    void getAvailablePorts()
    {            
        List<string> Itemlist = new List<string>();
        String[] ports = SerialPort.GetPortNames();
        Itemlist.AddRange(ports);
        comboBox1.ItemsSource = Itemlist;            
    }

    private void button1_Click_1(object sender, EventArgs e)
    {
        try
        {
            if (comboBox1.Text == "" || textBox6.Text == "")
            {
                MessageBox.Show("Please Select Port Settings");
            }
            else
            {
                serial.PortName = comboBox1.Text;
                serial.BaudRate = Convert.ToInt32(textBox6.Text); 
                serial.Parity = Parity.None;
                serial.StopBits = StopBits.One;
                serial.DataBits = 8;
                serial.Handshake = Handshake.None;
                serial.Open();
                MessageBox.Show("connected!");
            }
        }
        catch (UnauthorizedAccessException)
        {
            MessageBox.Show("Unauthorised Access");
        }
    }

    private void button2_Click_1(object sender, EventArgs e)
    {
        textBox1.Clear();
        textBox2.Clear();
        textBox3.Clear();
        textBox4.Clear();
        textBox5.Clear();
        MessageBox.Show("connection closed!");
        serial.Close();
        textBox1.Text = "test";
    }

    private void AppendText(string[] text)
    {
        try
        {             
                textBox1.Text = text[0];
                textBox2.Text = text[1];
                textBox3.Text = text[2];
                textBox4.Text = text[3];                
        }
        catch (Exception) { }
    }

    private void Safe_Position1(TextBox tBr1, TextBox tBi1, TextBox tBj1, TextBox tBk1, string[] text)
    {
        if (button3clicked == true)
        {               
                tBr1.Text = text[0];
                tBi1.Text = text[1];
                tBj1.Text = text[2];
                tBk1.Text = text[3];
                button3clicked = false;
        }
    }

    private void Safe_Position2(TextBox tBr2, TextBox tBi2, TextBox tBj2, TextBox tBk2, string[] text)
    {
        if (button4clicked == true)
        {                           
                tBr2.Text = text[0];
                tBi2.Text = text[1];
                tBj2.Text = text[2];
                tBk2.Text = text[3];
                button4clicked = false;               
        }
    }

    private void Safe_Position3(TextBox tBr3, TextBox tBi3, TextBox tBj3, TextBox tBk3, string[] text)
    {
        if (button5clicked == true)
        {              
                tBr3.Text = text[0];
                tBi3.Text = text[1];
                tBj3.Text = text[2];
                tBk3.Text = text[3];
                button5clicked = false;             
        }
    }

    private void Serial_DataReceived(object sender, SerialDataReceivedEventArgs e)
    {
        string serialData = serial.ReadLine();
        String[] text = serialData.Split(new char[] { ' ' });
        AppendText(text);
        Safe_Position1(textBox5, textBox7, textBox8, textBox9, text);
        Safe_Position2(textBox10, textBox11, textBox12, textBox13, text);
        Safe_Position3(textBox14, textBox15, textBox16, textBox17, text);
    }

    private void button3_Click(object sender, EventArgs e)
    {
        button3clicked = true;
    }

    private void button4_Click(object sender, EventArgs e)
    {
        button4clicked = true;
    }

    private void button5_Click(object sender, EventArgs e)
    {
        button5clicked = true;
    }
}

}

Do you want the function to set the text on all 4 textboxes? Or what would you like it to do? My AppendText function lets the textbox be variable. If you want to add the text to multiple textboxes just call: AppendText(textBox1, "whatever text"); AppendText(textBox2, "whatever text"); AppendText(textBox3, "whatever text"); — gunnerone, May 25 '18 at 15:08

C# display a variable in a Textbox

3 Answers3