How to import, View, export the files of format dwg and STP using c# in WPF Application?

We have tried
Aspose.3d
Anycad
Aspose.Cad
Helix Toolkit
LibreCad
Libre DWG
Teigha
Cad.NET
Opencascade

But we dont want to convert the files in other formats like jpg,tiff,pdf,svg or any format other than dwg and step
Need to retain the format as it is..

3d & 2D ViewPort showing the imported files without converting the files into other formats