Why can't my Debian VM on Hyper-V see the internet?

The VM works fine, but when I created it, I said "Set networking up later". Then, when I added an External Switch, connected to my host's Wifi adapter, and set it in the VM's networking settings, the VN would not start, and gave this error:

[Window Title]
Virtual Switch Manager for DESKTOP-D7J9MDT
[Main Instruction]
Error applying Virtual Switch Properties changes
[Content]
Failed while adding virtual Ethernet switch connections.
[Expanded Information]
Ethernet port '{6BD88402-616E-4574-81FE-147C20228D71}' bind failed: Catastrophic failure (0x8000FFFF).

Then I read somewhere I could use an internal switch and the VM would still have internet access. So I changed the switch to Internal, and now the VM starts and runs fine again, and gives no errors when I try to access the net, but it just aborts on a DNS name resolution failure.

The host is a Windows 10 Pro with all updated, and the guest is Debian 8.2

As you mentioned , internal virtual switch had been created .

You can configure ICS :

https://social.technet.microsoft.com/Forums/en-US/d380e4c3-a9c0-483f-8fd9-11962b1f486c/enable-virtual-machine-to-access-internet-with-ics?forum=winserverhyperv

In addition , if the VM still can not access internet , you can add "legacy network adapter" for that VM in VM settings , then try again .