Question: how to open vsdx file?
Answer: You need to install Microsoft Visio 2010 Service Pack 2 (SP2) or Microsoft Visio 2013 Viewer. I can confirm importing from VisualStudio 2013 (. VSDX) works very well, only some issue with lines but easy to correct. You can also use open it using LibreOffice Draw (tested on 4.3.