Why VS2019 get suddenly very slow and laggy while trying to debug a c# application?

Not sure whether the issue is caused your code with IDE environment together. Please try the following suggestions:

1) disable any third party installed extensions under Extensions-->Manage Extensions-->Installed to check whether an extension caused that.

2) reset settings under Tools-->Import and Export Settings-->Reset all settings and you can also make a backup of the settings

3) close VS, delete all files under C:\Users\xxx\AppData\Local\Microsoft\VisualStudio\16.0_xxx\ComponentModelCache

and also delete .vs hidden folder under your solution folder, bin and obj folder.

4) type devenv /safemode under Developer Command Prompt for VS to start a pure VS and then try your project.

5) create a new project with your same code and check if this works.

Besides, if all do not help, you could try a small reproducible sample with us.

If debugging suddenly becomes slow, you might consider checking your symbol settings and debugging settings. If you for example enable .NET framework source stepping, debugging can be slow, or if you do not cache symbols or disable for example Just My Code or enable other stuff, like IntelliTrace or install a bad extension.

It might not be an alternative for you, but I am pleased to inform you that I have been using Visual Studio 2022 and it is radically faster. Yes, this is not opinionated, this is an observation. It IS faster. Maybe it is because I do not have many extensions on it, but it is also a 64-bit application with less memory pressure on the GC. So you can first check your settings and then give VS 2022 Preview versions for a spin. I have used it for months and the amount of bugs are rather small if you do typically development. For a Preview version, I am impressed with what they are working for nextgen Visual Studio.

You should also clean your solution and delete and bin and obj folders via for example Powershell script to make sure your binaries are updated. Then rebuild.

If you have "live share" extension enabled, perhaps can try to disable / uninstall that. This one was causing my problem.

Ok, @Mr Qian no 3 did the trick for me.

Situation: After a "Cleanup" (Microsoft Visual Studio\Installer\InstallCleanup.exe) my VS2019 was partially gone. Good tool. :-(

After (re)install, I had 2 folders "ComponentModelCache" over 2 folders of 16.0_xxx : 16.0_4f678462 and 16.0_119826cb

I renamed both "ComponentModelCache" folders (you can delete later, when it has effect)

Build ran as never before...

Thank you, Mr Qian

My problems started as I upgraded to Visual Studio 2022 (from 2019) and upgraded to Windows 11 (naughty naughty, two major changes).

Turns out Windows Defender didn't preserve my exceptions. Using this PowerShell script as a template saved a bit of time: https://gist.github.com/Braytiner/be2497d1a06f5a9d943dc7760693d460

Performance is back to where is was pre my Windows 11/Visual Studio 2022 upgrade.

Visual studio 2019 (16.8.5) has this problem in debugging. I have updated it into 16.11.8 and it works properly.