ActiViz in WPF

In WPF, I wanted to lay out a ComboBox on RenderWindowControl, but failed. Is there any good way to do it? Other words, let the wpf control float on top of RenderWindowControl.

It is impossible. Look at this link https://learn.microsoft.com/en-us/dotnet/desktop/wpf/advanced/technology-regions-overview?view=netframeworkdesktop-4.8