I have a VSIX project. While trying to add a new command, or trying to add an asset to source.extension.vsixmanifest, I get the following error:

--------------------------- Microsoft Visual Studio --------------------------- VSIX Manifest Editor

The parameter is incorrect. (Exception from HRESULT: 0x80070057 (E_INVALIDARG)) --------------------------- OK

I tried to delete vs, bin, obj folders and clean C:\WINDOWS\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\

but still have this error. Also I ran Visual Studio with / Log but didn't find anything interesting.

Not sure whether your VS has something wrong. Please try the following steps:

1) disable any third party extensions under Extensions-->Manage Extensions--> Installed

2) try to run devenv /safemode under Developer Command Prompt for VS2019 to start a new pure VS to test whether the issue happens again.

3) delete all cache files under C:\Users\xxx\AppData\Local\Microsoft\VisualStudio\16.0_xxx(16.0 is VS2019 while 15.0 is VS2017)\ComponentModelCache

4) repair VS or update it to the latest version

Update 1

Reinstall VS and finally solve the issue.