How to Invoke / MethodInvoker call myself

Question

Addition after several closures of this question

NO, This question does not give the answer.

I tried it, I refer to it in my code, but it does not return from Invoke!

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Original question

Until now, whenever I had any other thread who had to update something on the UI, I used InvokeRequired / BeginInvoke in a pattern like this.

void UpdateLabel(string txt)
{
    if (this.InvokeRequired)
    {
        this.BeginInvoke(new MethodInvoker(delegate() { UpdateLabel(txt);}));
        return;
    }
    this.label1.Text = txt;
}

Test usage:

var task = Task.Run(() => UpdateLabel("Hello World!"));
task.Wait();

The first time InvokeRequired is true, the second time it is false;

But now I need to do this with a method that has a return value. StackOverflow to the rescue!

Answer states:

• Control.BeginInvoke: Executes on the UI thread, and calling thread doesn't wait for completion.
• Control.Invoke: Executes on the UI thread, but calling thread waits for completion before continuing.

And another question even gave an answer:

public static string readControlText(Control varControl)
{
    if (varControl.InvokeRequired)
    {
        return (string)varControl.Invoke(
               new Func<String>(() => readControlText(varControl)));
    }
    else
    {
        return varControl.Text;
    }
}

So I thought:

DialogResult AskPermission(string question)
{
    if (this.InvokeRequired)
    {
        return (DialogResult) this.Invoke(
                new MethodInvoker(delegate() { AskPermission(txt);}));
    }

    return MessageBox.Show(question, caption, MessageBoxButtons.YesNoCancel);
}

Alas, this does not work. First time InvokeRequired true, but no second time for InvokeRequired.

How to use Invoke / MethodInvoker?

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Addition after several closures of this question

Can it be that I call it incorrectly in my test code:

var task = Task.Run( () => AskPermission("What should I do?");
Dialogresult dlgResult = task.Wait();