using (var stream = File.Open(@"c:\temp\xDiagram.png", FileMode.Create))
xDiagram.ExportToImage(stream, backgroundBrush: new SolidColorBrush(Colors.BlanchedAlmond));
You can find more information here. Please note that the default Background of the RadDiagram in the Office_Black theme is Transparent.
Regarding the HTMLExportHelper class, you will be to copy and use it if you install our WPF demos. Let me know whether you would like me to send that class to you.
Pavel R. Pavlov
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