Debugging C# - VSCode hangs when breakpoint hit

[RandScullard]

Issue Type: Bug

• I am using VSCode to debug my C# ASP.NET Core project running on Kestrel on my Windows laptop.
• I set a breakpoint in my C# code and trigger the feature in my app (in the browser) that causes that breakpoint to be hit.
• I see VSCode's task bar button begin to flash, indicating that the breakpoint has been hit.
• I click the task bar button to bring VSCode to the foreground.
• VSCode is hung - the entire UI is non-responsive. The line with the breakpoint is not highlighted.
• I click back on the browser window and VSCode immediately becomes responsive again and highlights the line with the breakpoint. I can then work with the debugger, which works fine until the next time a breakpoint is hit; then the whole process repeats.

This sequence of steps happens the same way every time. I have tried a sample ASP.NET Core project and got the same behavior, so it is nothing specific to my code. I have also tried disabling all extensions except the C# extension (required for debugging) and it still happens.

VS Code version: Code 1.53.2 (622cb03, 2021-02-11T11:48:04.245Z)
OS version: Windows_NT x64 10.0.19042

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz (12 x 2592)
GPU Status	2d_canvas: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on oop_rasterization: enabled opengl: enabled_on protected_video_decode: enabled rasterization: enabled skia_renderer: enabled_on video_decode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled
Load (avg)	undefined
Memory (System)	31.71GB (18.94GB free)
Process Argv	--crash-reporter-id 28325b46-87fa-4884-ae6b-3bd5373edc01
Screen Reader	no
VM	67%

Extensions (11)

Extension	Author (truncated)	Version
vscode-sqlite	ale	0.11.1
awarest-align	awa	1.1.0
markdown-preview-github-styles	bie	0.1.6
vscode-eslint	dba	2.1.14
EditorConfig	Edi	0.16.4
rainbow-csv	mec	1.8.1
git-graph	mhu	1.28.0
csharp	ms-	1.23.9
powershell	ms-	2020.6.0
vscode-gitextensions	pmi	1.1.0
local-history	xyz	1.8.1

A/B Experiments

vsliv368:30146709
vsreu685:30147344
python383cf:30185419
vspor879:30202332
vspor708:30202333
vspor363:30204092
vstry244cf:30256637
pythonvsdeb440:30248342
pythonvsded773:30248341
vstes627cf:30244335
pythonvspyt875:30251590

[avenmore]

I'm also seeing this when a "debugger" statement is hit in my Vue script section. The behavior reminds me of my Win32 days when we would call LockWindowUpdate() while doing some messy painting to reduce flicker, and it didn't get unlocked. I'm now in the habit of doing a quick double Alt-Tab or double tapping the Windows key (to bring up/hide the Start menu) which has the effect of unlocking it.

[isidorn]

Sounds related to this #114459
Since we use the electron focus window API. Also assigning to @deepak1556 since he would know if we should close this as duplicate

[avenmore]

It certainly is the same issue as #116615 which was closed as a duplicate of #114459, and starting with code --disable-features=CalculateNativeWinOcclusion solves the problem for me too, so I would say yes, this is a duplicate of that issue.

[isidorn]

Thanks for letting us know. Then let's close as duplicate, and if @deepak1556 thinks I am mistaken we can reopen

[deepak1556]

Nope all good, thanks for triaging the issue!

[RandScullard]

Confirmed that code --disable-features=CalculateNativeWinOcclusion fixes the problem on my system. Thanks for your help!