C#•3mo ago

Trying to get started with threads but UI thread giving cross thread exceptions?

I have a thread that runs infinitely and what i believe is happening is that the new thread means events run on it leading to cross threading exceptions but i dont understand why that thread cant run in the background and events stay running on the main ui thread? This is the test i am using for my new thread

private void CalculateEngineOutput() //Calculate some of the main outputs
  {
      while (true)
      {
         

          RevoloutionSpeed = 100 * Throttle;


      }
  }

private void CalculateEngineOutput() //Calculate some of the main outputs
  {
      while (true)
      {
         

          RevoloutionSpeed = 100 * Throttle;


      }
  }

and my throttle event handler is giving me threading exceptions but its on the main ui thread right?

 private void TRACKBAR_Throttle_Scroll(object sender, EventArgs e) //The trackbar throttle value is changed
 {
     //Gets the trackbar throttle value and removes the idle value from it to find how much the throttle is actually open

     if (TRACKBAR_Throttle.Value/100 <= (double)MainForm.ACCESSOR_GrabEngineObject.ACCESSOR_ATTRB_IdleThrottlePosition/100) //If the value is less than the idle throttle position
     {
         Throttle = (double)MainForm.ACCESSOR_GrabEngineObject.ACCESSOR_ATTRB_IdleThrottlePosition/100; //Set it to the idle throttle position
     }
     else
     {
         Throttle = TRACKBAR_Throttle.Value / 100; //Otherwise set it to the actual scroll bar value
     }
 }

 private void TRACKBAR_Throttle_Scroll(object sender, EventArgs e) //The trackbar throttle value is changed
 {
     //Gets the trackbar throttle value and removes the idle value from it to find how much the throttle is actually open

     if (TRACKBAR_Throttle.Value/100 <= (double)MainForm.ACCESSOR_GrabEngineObject.ACCESSOR_ATTRB_IdleThrottlePosition/100) //If the value is less than the idle throttle position
     {
         Throttle = (double)MainForm.ACCESSOR_GrabEngineObject.ACCESSOR_ATTRB_IdleThrottlePosition/100; //Set it to the idle throttle position
     }
     else
     {
         Throttle = TRACKBAR_Throttle.Value / 100; //Otherwise set it to the actual scroll bar value
     }
 }

20 Replies

Nasdack•3mo ago

What is the exception saying?

MKMOP•3mo ago

{Value = {"Cross-thread operation not valid: Control 'TRACKBAR_Throttle' accessed from a thread other than the thread it was created on."} Min = 0 Max = 100} @Nasdack

Nasdack•3mo ago

TRACKBAR_Throttle is a UI control that is created from within the main thread What UI framework are you using?

MKMOP•3mo ago

winforms

Nasdack•3mo ago

Controls in WinForms provide an Invoke method so you that there you can execute actions on the thread from which they were created

MKMOP•3mo ago

okay so would i have to modify every single one of my methods and invoke them?

Nasdack•3mo ago

No I'm on my phone What you can do Is wrap the whole event handler method With TRACKBAR_Throttle.Invoke(() => { // existing method code});

MKMOP•3mo ago

would i do this for all events?

Nasdack•3mo ago

Any event that creates its own thread, yes

MKMOP•3mo ago

sorry just to make sure so i have this calculation thread and everything else on the ui thread, and so all events that need to be on ui thread need to be invoked because they canbe called whilst the calculation thread is running

Nasdack•3mo ago

If your calculation is running in its own thread, and it tries to invoke an event, that event will run on the thread that of the calculation logic, not that of the UI.

MKMOP•3mo ago

ah okay so i must invoke all my ui events becuase the calculation thread is always running is there a cleaner way to do this or is that it

Nasdack•3mo ago

Not all of them, just the ones that are invoked by the calculation thread. What's unclean about it?

MKMOP•3mo ago

the calculation thread doesnt invoke any though so im confused they can be invoked whilst the calculation thread is running but not by it

Nasdack•3mo ago

That is weird Not sure why But that fixes your problem anyway

MKMOP•3mo ago

okay thank you very much ill try that now

Nasdack•3mo ago

MKMOP•3mo ago

@Nasdack

Nasdack•3mo ago

there's a multitude of overloads your syntax is most likely incorrect

Nasdack•3mo ago

Send the rest of the code

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Trying to get started with threads but UI thread giving cross thread exceptions?

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