Hi i have the same problem, I work with WIndows 7 x64 and Windows 10 x64
The problem is that dont show any webcam using Direct Show.
The problem started on 28 may of 2017 i think that with an update after midday

Avast doest now show anything but in passive mode , starts working all again (i have to restart the pc).
if i unnistall avast and restart the pc all start working again.
Any application working with directshow does not work Probably written in c# .net winforms or wpf (i have tryed both).

Here its a code with binary excutable example https://www.codeproject.com/Articles/671407/Camera-Net-Library

Binary https://www.codeproject.com/KB/audio-video/671407/Camera_Net_Samples._Compiled.NET4.__v1.1.2_.zip (you must to get login in codeproject)