I am new to C# and am looking for some advice on an issue I have been trying to solve in my Windows Form application.
I have an application that needs to continuously read data coming back to the program over a connected serial port. I have buttons that Open and Close the port via the user. I am having trouble configuring the "DataReceived" event handler to read the incoming data and display it in a textbox in the app.
I have been getting this error: "Cross-thread operation not valid: Control 'textBox4' accessed from a thread other than the thread it was created on." I see this is a thread error but I have not been able to figure out my issue.
namespace Program
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
getAvailabePorts();
}
private void getAvailabePorts()
{
String[] ports = SerialPort.GetPortNames();
comboBox1.Items.AddRange(ports);
}
public void button1_Click(object sender, EventArgs e)
{
try
{
if (comboBox1.Text == "" || comboBox2.Text == "")
{
textBox4.Text = "Please select port settings";
}
else
{
serialPort1.PortName = comboBox1.Text;
serialPort1.BaudRate = Convert.ToInt32(comboBox2.Text);
serialPort1.DataReceived += new SerialDataReceivedEventHandler(mySerialPort_DataReceived);
serialPort1.Open();
}
}
catch (UnauthorizedAccessException)
{
textBox4.Text = "Unauthorized Access";
}
public void mySerialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
SerialPort sp = (SerialPort)sender;
textBox4.Text = sp.ReadExisting() + "\n";
}
private void button2_Click(object sender, EventArgs e)
{
serialPort1.Close();
textBox4.Clear();
}
}
}
}
First, welcome.
Before the "big" issue (marshalling data), let me warn you -- serial ports are tricky. For example, your call to "ReadExisting" may not return what you expect -- will return whatever is in the serial port buffer at the time, but more may come in, which will overwrite what is already in your text box. So you may want to append data your text box.
Now the real issue. As a commentor mentioned, you cannot post directly post data from another thread to the UI thread. Without you knowing, the serial port created a new thread to receive data.
You can handle this directly by modifying your receiver code as follows:
public void mySerialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
SerialPort sp = (SerialPort) sender;
var dataRcvd = sp.ReadExisting();
object[] dataArray = new object[1];
dataArray[0] = dataRcvd;
BeginInvoke( new postDataDelegate( postData), dataArray );
}
private delegate void postDataDelegate( string d );
private void postData( string d)
{
textBox4.Text = d;
}
This will "marshall" the data to the UI thread so it can be used. There are many ways this can be done (and, many differences between how it is done in WPF vs. Winforms, so watch out for that). I hope this illustrates the point.
Another aside -- no need ot make the DataReceived method public -- it will work fine private.
Related
I am building a device controller in C# that controls the flow rate of pumps. There is Form1 and a Pump-Class, holding all properties and methods of the pump that are accessible through the Form. So far, everything works fine. However, there might be the case where there is more than one pump. Of course, I could run individual instances of the executable, but you know..
How can I create multiple instances of the pump-class according to my current demand. Maybe an extra Form upfront with an Add-Button, where it is possible to create as much pumps as needed?
Sure, this is comes down to a very basic question, but I am no professional programmer.. Any comments are highly appreciated.
Thanks in advance.
mulm
namespace PumpController
{
public partial class Form1 : Form
{
static Pump pump;
public Form1()
{
InitializeComponent();
cb_availablePorts.DropDownStyle = ComboBoxStyle.DropDownList;
cb_baudRates.DropDownStyle = ComboBoxStyle.DropDownList;
string[] availablePorts = SerialPort.GetPortNames();
foreach (string item in availablePorts)
{
cb_availablePorts.Items.Add(item);
}
string[] commonBaudRates = new string[] { "4800", "9600", "19200", "38400", "57600", "115200" };
foreach (string item in commonBaudRates)
{
cb_baudRates.Items.Add(item);
}
}
private void bt_valueUp_Click(object sender, EventArgs e)
{
if (!(pump == null))
{
pump.increaseValue();
}
}
private void bt_valueDown_Click(object sender, EventArgs e)
{
if (!(pump == null))
{
pump.decreaseValue();
}
}
private void Form_Closing(object sender, EventArgs e)
{
Hide();
if (!(pump == null))
{
pump.Close();
}
}
private void bt_connect_Click(object sender, EventArgs e)
{
if (!(cb_availablePorts.SelectedItem == null) && !(cb_baudRates.SelectedItem == null))
{
Pump pump = new Pump(Convert.ToString(cb_availablePorts.SelectedItem), Convert.ToInt32(cb_baudRates.SelectedItem));
}
}
}
}
The comments lead to part of the answer and are right as far as they go. However, one important thing has perhaps been overlooked -- the part about finding an(other) COM port.
Each time you instantiate a new Pump object, and add it to the List<Pump> collection, these objects will contend for the same COM port unless you allocate another port.
There is a well-accepted answer for this at enumerating COM ports. Hate to provide a link as the heart of my answer, but if you have a four-object list of Pump objects contending for a single serial port, you could have troubles.
I have one device "installed" on a users desk (a desk is nothing but a chair or table on which user will sit), and I will be supporting thousands of desks.
A user will have one "chip" and the user will scan this chip on the device which is installed on their desk.
The device will read the data off the chip and will send it to my laptop which will also have one of the devices installed, except this device is the main device responsible for collecting all user scan chip data.
All the data will be routed to my device via a wifi router and I will listen to this from my Main device and read data from this device from my laptop via serial port connection.
This data sending will happen as each user number scans his/her chip.
I have created a windows form application which will continuously run in the background on my laptop, and will be listening to my serial port on which main device is connected.
This is my code taken from here: Source Code Reference:
public partial class MainUI : Form
{
SerialPortManager _spManager;
public MainUI()
{
InitializeComponent();
UserInitialization();
}
}
private void UserInitialization()
{
_spManager = new SerialPortManager();
_spManager.NewSerialDataRecieved += new EventHandler<SerialDataEventArgs>(_spManager_NewSerialDataRecieved);
this.FormClosing += new FormClosingEventHandler(MainUI_FormClosing);
}
private void MainUI_Load(object sender, EventArgs e)
{
_spManager.StartListening()
}
void _serialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
int dataLength = _serialPort.BytesToRead;
byte[] data = new byte[dataLength];
int nbrDataRead = _serialPort.Read(data, 0, dataLength);
if (nbrDataRead == 0)
return;
// Send data to whom ever interested
if (NewSerialDataRecieved != null)
{
NewSerialDataRecieved(this, new SerialDataEventArgs(data));
}
}
void _spManager_NewSerialDataRecieved(object sender, SerialDataEventArgs e)
{
if (this.InvokeRequired)
{
// Using this.Invoke causes deadlock when closing serial port, and BeginInvoke is good practice anyway.
this.BeginInvoke(new EventHandler<SerialDataEventArgs>(_spManager_NewSerialDataRecieved), new object[] { sender, e });
return;
}
//data is converted to text
string str = Encoding.ASCII.GetString(e.Data);
if (!string.IsNullOrEmpty(str))
{
//Here i will store that data in to my database through web service.
//What i should use whether WCF service or Web Api because data will be continuos like at a
//time more than 10 or 100 user can scan data at the same time so this event will be fired continuously.
//I am using entity framework to store data in to my database and how to ansynchornously call web service to store my data
//so that my call doesnt block incoming data to serial port
}
}
My main concern is I will have numerous users who will scan data at the same time and how I will handle when more than 10 or 100 user scan the data at the same time.
How can I mitigate this potential issue?
Ok, if i got the question right you need to do something like this ...
void _serialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
int dataLength = _serialPort.BytesToRead;
byte[] data = new byte[dataLength];
int nbrDataRead = _serialPort.Read(data, 0, dataLength);
if (nbrDataRead == 0)
return;
// Send data to api
string str = Encoding.ASCII.GetString(e.Data);
if (!string.IsNullOrEmpty(str))
{
var api = new HttpClient();
api.BaseUrl("http://somewhere.com");
api.PostAsJsonAsync("api/Something", str)
}
if (this.InvokeRequired)
{
// Using this.Invoke causes deadlock when closing serial port,
// and BeginInvoke is good practice anyway.
this.BeginInvoke(new EventHandler<SerialDataEventArgs>(
_spManager_NewSerialDataRecieved), new object[] { sender, e
});
return;
}
}
// i think this can go completely ...
void _spManager_NewSerialDataRecieved(object sender, SerialDataEventArgs e)
That posts the data to webapi but whilst that post is taking place on another thread the serial port can carry on receiving data
close your serial port and load every some-amount-of-time. After that some-amount-of-time open the port and scan all devices, then close it again.
public void MainUI.Load(Object sender, Eventargs e)
{
if (_spmanager != null && !_spManager.IsOpen)
//*write the code here where it opens and starts listening
_spmanager.StartListening();
//*write the code here where it waits a little bit then
_spmanager.Close();
}
Therefore everytime it loads it starts when the port is closed, it opens for a little bit, scans whatever values are true and then closes again.
I am not very sure about this but it is just an idea of how to handle it. The code might not be accurate or currect I just wrote it quickly. Take the idea from this
All these comes from the idea that i want to use the SerialPort class in .Net , but the only way is by calling dll . Because i can only get interfaces from the program calling this dll. mycode is below.
i wrote a class about serialport,
public class CommClass
{
public SerialPort _port;
private string _receivedText;
public string receivedText
{
get { return _receivedText; }
set
{
_receivedText = value;
}
}
public CommClass(string _pname)
{
portList = SerialPort.GetPortNames();
_port = new SerialPort(portList[0]);
if (portList.Length < 1)
_port= null;
else
{
if(portList.Contains(_pname.ToUpper()))
{
_port = new SerialPort(_pname);
_port.DataReceived += new SerialDataReceivedEventHandler(com_DataReceived);
}
}
}
private void com_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
string indata = _port.ReadExisting();
receivedText = indata;
}
}
from Bytestoread i can see there r data coming in and i can get data from port.ReadExisting(), but receivedText did not change ,it did not hit the SerialDataReceived event . Is my way wrong?any suggestion?thanks
i created a dll from CommClass ,then i call it in my winform program which has a button and a textbox . Clicking the button , then i initialize the port
public Form1()
{
InitializeComponent();
}
public CommClass mycom;
private void button1_Click(object sender, EventArgs e)
{
mycom = new CommClass("com3");
mycom._port.Open();
textbox.Text=mycom.receivedText;//i add a breakpoint at this line ,
}
when hitting it , i check mycom._port.PortName is "com3", its IsOpen() is "Open" , i use virtual port to send data . i send "1111",then check the mycom._port.BytestoRead is 4, and mycom._port.ReadExisting() is "1111", but mycom.receivedText is null. My puzzle is that i have no idea when the data is coming . How to use the DataReceived event in my winform without code "using System.Io.Ports",just with reference CommClass.dll. Did i make it clear? Thanks for help.
mycom._port.Open();
textbox.Text=mycom.receivedText;//i add a breakpoint at this line ,
That code cannot work, it is a threading race bug. The DataReceived event does not fire instantly after you open the port. It will take a microsecond or so, give or take. A threadpool thread has to get started to fire the event. And of course the device actually has to send something, they usually only do so when you transmit something first.
Which clearly did not happen, your DataReceived event handler has a bug as well. It is not allowed to update the Text property of a control in that event since it runs on a worker thread. Your program will bomb with an InvalidOperationException.
You'll have to write something like this instead:
private void com_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
string indata = _port.ReadExisting();
this.BeginInvoke(new Action(() => {
textbox.AppendText(indata);
}));
}
With the additional stipulation that you must not leave it this way, updating the Text property of a TextBox and making it visible on the screen is an expensive operation that's going to turn your user interface catatonic when the device starts transmitting data at a high rate.
So, I'm trying to develop a simple application in visual C# which gets data from serial port and displays it in a textbox (to monitor temperature). I'm acquiring and displaying the data successfully, using the DataReceived event to update a global string variable and a timer to update the text field on my text box, as shown:
private void port_DataReceived_1(object sender, SerialDataReceivedEventArgs e)
{
try
{
globalVar.updateTemp = port.ReadLine(); //This is my global string
}
catch (IOException)
{
}
catch (InvalidOperationException)
{
}
catch (TimeoutException)
{
}
}
private void timer1_Tick(object sender, EventArgs e)
{
tempDisplayBox.Text = globalVar.updateTemp; //This is my textbox updating
}
The only issue I have is that the value shown in the textbox keeps flashing, making it hard to read. My timer is set to trigger every 10 ms (which should be fast enough, right?). Is there any way to make it more stable? I realize this may be a newb question, but to be fair I am a newb :) Any help is appreciated! Thanks!
Do you really need it updating every 10ms? What about every 500 ms or if not that then 100ms. 100ms will require your update method run 10 times less and therefore update 10 times less. The flickering you are expiriencing is due to the refresh speed. You could create custom method which will only update the temp only when target Label or textBox value is different than source port. But that will only sort the flickering when temp is steady, when temp will start vary it will bring back the flickering. Good luck ;-)
UPDATE
Hi I tried to reproduce the conditions and could not make my textbox nor Label flash. The way I tested it was by assigning int ntick = 0; and then increment the ++ntick; inside of the timer_tick method. The results didn't make any of the controls flash and were updated even every milisecond at some point. I also tried string.Format to put some load on the method. Is your app responsive?
The trick is to use double buffering. This way the operating system will redraw the Control off-screen, and only show the control when it is fully redrawn.
I have had the same problem, and solved it by extending the TextBox control like this:
public FastLogBox()
{
InitializeComponent();
_logBoxText = new StringBuilder(150000);
timer1.Interval = 20;
timer1.Tick += timer1_Tick;
timer1.Start();
SetStyle(ControlStyles.DoubleBuffer, true);
}
void timer1_Tick(object sender, EventArgs e)
{
if (_timeToClear)
{
_logBoxText.Clear();
_timeToClear = false;
}
if (_logQueue.Count <= 0) return;
while (!_logQueue.IsEmpty)
{
string element;
if (!_logQueue.TryDequeue(out element)) continue;
{
_logBoxText.Insert(0, element + "\r\n");
}
}
if (_logBoxText.Length > 150000)
{
_logBoxText.Remove(150000, _logBoxText.Length - 150001);
}
Text = _logBoxText.ToString();
}
public new void Clear()
{
_timeToClear = true;
while (!_logQueue.IsEmpty)
{
string element;
_logQueue.TryDequeue(out element);
}
}
public void AddToQueue(string message)
{
_logQueue.Enqueue(message);
}
}
I also use a timer and a concurrentQueue to avoid using Invoke to update the control from another thread. I also use a StringBuilder to prepare the string before putting it into the TextBox. StringBuilder is faster when building larger strings.
You can use ReadExisting() to read the whole data at a time.
You need to handle DataReceived Event of SerialPort
serialPort1.ReadExisting();
Sample:
private void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
String myData=serialPort1.ReadExisting();
}
Example Code: Here i would like to show you the code to Read Data(RFID Tag Code which is basically of length 12)
String macid = "";
private void DoWork()
{
Invoke(
new SetTextDeleg(machineExe ),
new object[] { macid });
macid = "";
}
private void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
string str1;
macid += serialPort1.ReadExisting();
if (macid.Length == 12)
{
macid = macid.Substring(0, 10);
Thread t = new Thread(new ThreadStart(DoWork));
t.Start();
}
}
public void machineExe(string text)
{
TextBox1.Text=text;
}
Thank you so much for the answers! I found a way to work around this issue:
Instead of replacing the contents of my textbox by rewriting the TextBox.Text property - which, as HenningNT implied, refreshes the control and causes the flickering - I'm now using the TextBox.AppendText method. Though, as I want to display only one line of data at a time, I use the textbox in multiline mode and the Environment.NewLine to jump to a new line before appending the text. As for the method of updating, I've gone back to using the timer because with the invoke method was crashing my application when I close the form, for some reason. Also, enabling double buffering didn't do me much good, although I guess I was doing it wrong... It still flickers a bit, but it's much better now :) I know this is not really a perfect solution (much more of a workaround), so I'll keep looking for it. If I find it, I'll be sure to update it here ;) My code:
private void timer1_Tick(object sender, EventArgs e) //Timer to update textbox
{
if (tempDisplayBox.Text != globalVar.updateTemp) //Only update if temperature is different
{
try
{
tempDisplayBox.AppendText(Environment.NewLine);
tempDisplayBox.AppendText(globalVar.updateTemp);
}
catch (NullReferenceException)
{
}
}
}
I am developing a C# application to make and receive calls from a GSM modem. I am using a timer_tick event to regularly read the port using port.ReadExisting() and comparing it with RING. If there is a match, display in a label that there is an incoming call. However I couldn't get it to work. Looking for suggestions.
I solved the problem. Cheers. This is the code that i wrote.. Might help some one
private void timer1_Tick(object sender, EventArgs e)
{
if (port.IsOpen)
{
string s = port.ReadExisting();
if (s.Contains("\r\nRING\r\n"))
{
incall_status.Text = "Incoming Call....";
incall_status.Visible = true;
}
else if (s.Contains("\r\nNO CARRIER\r\n"))
{
incall_status.Text = "Call Disconnected";
bgwrkr_calldisconect.RunWorkerAsync();
}
}
}