fix XamlExporter in Exporters
fix XamlExporter in Exporters

jotschgl/helix-toolkit,CobraCalle/helix-toolkit,Iluvatar82/helix-toolkit,smischke/helix-toolkit,chrkon/helix-toolkit,holance/helix-toolkit,helix-toolkit/helix-toolkit,JeremyAnsel/helix-toolkit