在创建窗口句柄之前，无法在控件上调用Invoke或BeginInvoke

Question

hey guys I get this exception when my application closes. CustomerReadySub is an event that I have subscribed to.

The error happens on this line

fTypeLabel.Invoke(new MethodInvoker(fuelTypeChosen));

public void CustomerReadySub(object sender, CustomerReadyEventArgs fuel)
    {
            // code to handle the event
            string CustReady = null;

            //checks what fuel is chosen and then activates the pump
            fuelType = fuel.SelectedFuel.ToString();

            if (!String.IsNullOrEmpty(fuelType))
            {
                fTypeLabel.Invoke(new MethodInvoker(fuelTypeChosen));

                if (fuelType == "Unleaded") //checks fuel type and displays price accordingly
                {
                    pplText.Invoke(new MethodInvoker(petrol));
                }
                else
                {
                    pplText.Invoke(new MethodInvoker(diesel));
                }

                CustReady = "READY";
                WCFPump.sendReady(CustReady);
            }

            while (WCFPump.getOK() == 0) { /*do nothing*/} //used to loop around until OK is retrieved
            if (pumpID == WCFPump.getOK())
            {
                CustGen.ActivatePump();
            }

    }

    private void fuelTypeChosen()
    {
        fTypeLabel.Text = fuelType;
    }

I am not really sure what is causing the problem.

Answer 1

The error seems quite clear, except for the 'until' part when you are already closing down. I think you can also read it as "Invoke or BeginInvoke cannot be called on a control after the window handle has been destroyed "

So your event fires after the Window has been destroyed. The actual code responsible for that is not posted but the code we do see is really happy to do busy-waiting. So apparently you are disturbing the Windows event mechanism enough to cause this timing problem.

Short fix:

      if (! fTypeLabel.IsHandleCreated) return;  // emergency exit
      fTypeLabel.Invoke(new MethodInvoker(fuelTypeChosen));

but you should really consider fixing the synchronous nature of your code. Uses events and async.