XPS 8940's S USB C port is designed for Data transfer only  Means you can connected USB C flash drives. External hard drives only  Typical Laptop USB C functionalities such as Docking stations, Monitors, Cellphone won't work on it.   Being a desktop it has plethora of options to connect peripherals, monitors.  Anyways it has USB 3.1 ports so USB C is not giving you any additional advantage,     
I just received a 5th gen iPad Pro and tried connecting it to my XPS 8940 USB Type-C port using the supplied Apple USB-C type cable.  I get an error message that states "An incompatible device was connected to your USB port. Your port is intended to be used with USB data devices only.". If I use a USB Type-C to type USB-A adapter and plug it into a standard USB port on the XPS 8940, the iPad connects just fine. I thought the XPS 8940 USB Type-C port should work just fine. Has anyone else encountered this issue? What am I missing? Edit: To clarify, I used a different cable that has a USB Type-C on one end to USB-A on the other end. The original Apple supplied cable works for charging the iPad. Could it be that the problem is not with the XPS 8940 and the Apple cable is not a data cable (charging only)? Or the Apple cable is data defective? Looking for someone that has these devices and can confirm their results.
XPS 8940, USB Type-C port won't connect with iPad Pro