Why would InvokeRequired=False via a Delegate.BeginInvoke?

Question

For what reasons would this.InvokeRequired equal False within InitUIState(), as this new thread is being created via a delegate?

My problem is that my label is never being set and this.BeginInvoke() is never executing, I imagine it's due to the fact InvokeRequired = False.

    private delegate void BackgroundOperationDelegate(ViewMode mode);
    private BackgroundOperationDelegate backgroundOperationDelegate;

    private void FormControlPanel_Load(object sender, EventArgs e)
    {
        Init();
    }

    private void Init() {
        this.backgroundOperationDelegate = this.InitUIState;
        this.backgroundOperationDelegate.BeginInvoke(mode, null, null);
    }

    private void InitUIState(ViewMode mode)
    {
        // .. other business logic only here relevant
        // to the worker process ..
        this.BeginInvoke((MethodInvoker)delegate
        {
            this.labelProgramStatus.Text = CONSOLE_IDLE_STATUS;
        });
    }

I use this pattern time and time again, but for some reason, this time it's not executing :P (and yes there is only one instance of InitUIState() ever being called, that being from the delegate)

Thanks guys.

Images verifying two distinct threads:
http://imgur.com/mq12Wl&X5R7G
http://imgur.com/mq12W&X5R7Gl

Follow up question: Is this an unpreferred way of creating threads? I've just always found it so simple and lightweight. Perhaps I should be using thread.Start() and I will avoid these issues?

Answer 1

Invoke and BeginInvoke on delegates are not the same as ISynchronizeInvoke.

Also you need to call EndInvoke when dealing with a delegate.

Answer 2

You are mixing BeginInvoke of Form and Delegate, as both of them have same method name.

Form's method, BeginInvoke calls the method you are requested in the same UI thread, but on a later stage, after processing its own pending UI operations. This is the reason, InvokeRequired will always be false within the Form's BeginInvoke's method.

Delegate's method, BeginInvoke calls the method on a new thread asynchronously in thread pool. And InvokeRequired in delegate's BeginInvoke will always be true.

Answer 3

Your 2nd BeginInvoke will throw an Exception.

Try

private void InitUIState(ViewMode mode)
{
    if (this.InvokeRequired)
    {
        this.BeginInvoke((MethodInvoker)delegate
        {
            InitUIState(mode);
        });
    }
    else
    {
        this.labelProgramStatus.Text = CONSOLE_IDLE_STATUS;
    }
}