Cross-thread operation not valid Control textBox1 accessed from a thread other than the thread it was created on

Question

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

User · Answer

I don t know if this is good enough but I 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            lt summary gt          Set text property of various controls          lt  summary gt           lt param name  form  gt The calling form lt  param gt           lt param name  ctrl  gt  lt  param gt           lt param name  text  gt  lt  param gt      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

User · Answer

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

User · Answer

Use a shared container to transfer data between threads

User · Answer

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           lt summary gt          Helper method to determin if invoke required  if so will rerun method on correct thread          if not do nothing           lt  summary gt           lt param name  c  gt Control that might require invoking lt  param gt           lt param name  a  gt action to preform on control thread if so  lt  param gt           lt returns gt true if invoke required lt  returns gt      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       gt  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       gt  UpdateControl c s    return          myControl Text   s          myControl BackColor   c

User · Answer

Use the following extensions and just pass the action like     frmx PerformSafely      gt   frmx Show      frmx PerformSafely      gt   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 lt T1 gt  this Control target  Action lt T1 gt  action T1 parameter                if  target InvokeRequired                        target Invoke action  parameter                     else                       action parameter                        public static void PerformSafely lt T1 T2 gt  this Control target  Action lt T1 T2 gt  action  T1 p1 T2 p2                if  target InvokeRequired                        target Invoke action  p1 p2                     else                       action p1 p2

User · Answer

you can simply do this   TextBox CheckForIllegalCrossThreadCalls   false

[c#] Cross-thread operation not valid: Control 'textBox1' accessed from a thread other than the thread it was created on

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