Why is proxy not intercepting requests from my .NET 4.8 app

To use devproxy with .NET 4.8, you need to configure it as proxy with the WinHTTP API.

Use the netsh command to configure the proxy. (run as admin):

netsh winhttp set proxy proxy-server="http=localhost:8000;https=localhost:8000"

When you're done, you can reset the WinHTTP settings by using:

netsh winhttp reset proxy