This question already has an answer here:
I want to send temperature value from a microcontroller using UART to C# interface and Display temperature on Label.Content. Here is my microcontroller code:
while(1) {
key_scan(); // get value of temp
if (Usart_Data_Ready())
{
while(temperature[i]!=0)
{
if(temperature[i]!=' ')
{
Usart_Write(temperature[i]);
Delay_ms(1000);
}
i = i + 1;
}
i =0;
Delay_ms(2000);
}
}
and my C# code is:
private void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
txt += serialPort1.ReadExisting().ToString();
textBox1.Text = txt.ToString();
}
but exception arises there "Cross-thread operation not valid: Control 'textBox1' accessed from a thread other than the thread it was created on" Please tell me how to get temperature string from my microcontroller and remove this Error!
The data received in your serialPort1_DataReceived method is coming from another thread context than the UI thread, and that's the reason you see this error.
To remedy this, you will have to use a dispatcher as descibed in the MSDN article:
How to: Make Thread-Safe Calls to Windows Forms Controls
So instead of setting the text property directly in the serialport1_DataReceived method, use this pattern:
delegate void SetTextCallback(string text);
private void SetText(string text)
{
// InvokeRequired required compares the thread ID of the
// calling thread to the thread ID of the creating thread.
// If these threads are different, it returns true.
if (this.textBox1.InvokeRequired)
{
SetTextCallback d = new SetTextCallback(SetText);
this.Invoke(d, new object[] { text });
}
else
{
this.textBox1.Text = text;
}
}
So in your case:
private void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
txt += serialPort1.ReadExisting().ToString();
SetText(txt.ToString());
}
if (this.InvokeRequired) { //SetTextCallBack etc. } instead of if (this.textBox1.InvokeRequired) { //SetTextCallBack etc. } - Jroonkcontrol.BeginInvoke work too? the solution can be 1 line too like this, right? textbox1.BeginInvoke((MethodInvoker)delegate(){ textbox1.Text = txt.ToString(); }); - newbieguySetTextCallback works to invoke SetText is that you pass in SetText to new SetTextCallback(). DUHHH. - ErikE
I don't know if this is good enough but I did made a static ThreadHelperClass class and implemented it as following .Now I can easily set text property of various controls without much coding .
public static class ThreadHelperClass
{
delegate void SetTextCallback(Form f, Control ctrl, string text);
/// <summary>
/// Set text property of various controls
/// </summary>
/// <param name="form">The calling form</param>
/// <param name="ctrl"></param>
/// <param name="text"></param>
public static void SetText(Form form, Control ctrl, string text)
{
// InvokeRequired required compares the thread ID of the
// calling thread to the thread ID of the creating thread.
// If these threads are different, it returns true.
if (ctrl.InvokeRequired)
{
SetTextCallback d = new SetTextCallback(SetText);
form.Invoke(d, new object[] { form, ctrl, text });
}
else
{
ctrl.Text = text;
}
}
}
Using the code:
private void btnTestThread_Click(object sender, EventArgs e)
{
Thread demoThread =
new Thread(new ThreadStart(this.ThreadProcSafe));
demoThread.Start();
}
// This method is executed on the worker thread and makes
// a thread-safe call on the TextBox control.
private void ThreadProcSafe()
{
ThreadHelperClass.SetText(this, textBox1, "This text was set safely.");
ThreadHelperClass.SetText(this, textBox2, "another text was set safely.");
}
That's awesome solution, the most awesome thing is "it's open for extension and generic". you can simply add new UI update functions as you wish, thank you - Basheer AL-MOMANI
you can simply do this.
TextBox.CheckForIllegalCrossThreadCalls = false;
Use the following extensions and just pass the action like:
_frmx.PerformSafely(() => _frmx.Show());
_frmx.PerformSafely(() => _frmx.Location = new Point(x,y));
Extension class:
public static class CrossThreadExtensions
{
public static void PerformSafely(this Control target, Action action)
{
if (target.InvokeRequired)
{
target.Invoke(action);
}
else
{
action();
}
}
public static void PerformSafely<T1>(this Control target, Action<T1> action,T1 parameter)
{
if (target.InvokeRequired)
{
target.Invoke(action, parameter);
}
else
{
action(parameter);
}
}
public static void PerformSafely<T1,T2>(this Control target, Action<T1,T2> action, T1 p1,T2 p2)
{
if (target.InvokeRequired)
{
target.Invoke(action, p1,p2);
}
else
{
action(p1,p2);
}
}
}
Along the same lines as previous answers, but a very short addition that Allows to use all Control properties without having cross thread invokation exception.
Helper Method
/// <summary>
/// Helper method to determin if invoke required, if so will rerun method on correct thread.
/// if not do nothing.
/// </summary>
/// <param name="c">Control that might require invoking</param>
/// <param name="a">action to preform on control thread if so.</param>
/// <returns>true if invoke required</returns>
public bool ControlInvokeRequired(Control c,Action a)
{
if (c.InvokeRequired) c.Invoke(new MethodInvoker(delegate { a(); }));
else return false;
return true;
}
Sample Usage
// usage on textbox
public void UpdateTextBox1(String text)
{
//Check if invoke requied if so return - as i will be recalled in correct thread
if (ControlInvokeRequired(textBox1, () => UpdateTextBox1(text))) return;
textBox1.Text = ellapsed;
}
//Or any control
public void UpdateControl(Color c,String s)
{
//Check if invoke requied if so return - as i will be recalled in correct thread
if (ControlInvokeRequired(myControl, () => UpdateControl(c,s))) return;
myControl.Text = s;
myControl.BackColor = c;
}
Use a shared container to transfer data between threads.