GraphicsLayer.ToBitmap() issue

Question

If I create a graphic, add it to the GraphicsLayer and call GraphicsLayer.ToBitmap(), there is no my new graphic in the bitmap.
If I call ToBitmap later (using timer, for example), then the graphic is there.
It looks like the rendering of GraphicsLayers is async.
Is there any event that is rised when a GraphicsLayer is rendered? How to know when I can call ToBitmap?

Thanks in advance.

DenisT · Answer

Thank you.

DominiqueBroux · Answer

Dispatcher not worked for me.

Right. But 2 levels of dispatcher look working:
Dispatcher.BeginInvoke(() => Dispatcher.BeginInvoke(CreateBitmap));

Don't ask me why:confused:  but that may be a workaround. 
I don't know any other event to do that. You may try CompositionTarget.Rendering but likely not a good solution either.

DenisT · Answer

Dispatcher not worked for me.
I have attached a simple VS-solution, that shows a problem.

There are two main buttons.

"ToBitmap" button creates a new graphic, refreshes a GraphicsLayer and calls GraphicsLayer.ToBitmap().
There will be no new graphic point in the bitmap.

"ToBitmap() delayed" button will add a new graphic, make a delay using DispatcherTimer and then call GraphicsLayer.ToBitmap().
It works. However you never know how long the graphics layer refreshes itself.

SilverlightMapExportTest.zip

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