Hi,

Had to do a complete re-install of my OS and of course also re-install VS2022 and VisualMicro (very latest version). 

Now trying to build my project again. My project uses a number of libraries, for example 'SHT31-0.5.0', I'll focus on this one but the same applies to the other ones.

Using the Library Manager in VisualMicro Explorer I have installed that very library and indeed the 'SHT31-0.5.0.zip' file now appears in my '%APPDATA%\Local\arduino15\staging\libraries' folder and in my 'Documents\Arduino\libraries' folder there is a subfolder 'SHT31', it also appears in the dropdownbox at vMicro->Add Library->User Installed. So far so good I would think.

Yet when I load my project.sln in Solution Explorer it says 'SHT31-0.5.0 (not found). When I right-clight it and select 'Reload Project' I get a message 'The project file 'Documents\Arduino\libraries\SHT31\SHT31-0.5.0.vcxitems' has been moved, renamed or is not on your computer'.

And indeed it is not. In the SHT31 folder are simply the contents of the zip file, and in the zip file is no file with a .vcxitems extension.

I do have a backup of my 'Documents\Arduino\libraries\SHT31' folder from before the new OS and that backup does have the required SHT31-0.5.0.vcxitems file. Now of course I can restore this file from that backup but I want to understand what is going on. Where does the .vcxitems file come from? Was it at some point generated by VS2022? Or VisualMicro? 

Google tells me .vcxitems are 'Share Items Project' files. In 'vMicro->Add Library->Library Advanced' there is an option 'Create Shared Project When Including Libraries', I though maybe that is what I need but selecting that option gives me a warning 'Creating shared projects for libraries is not recommended in most cases......... Would you still like to enable this Feature? Yes/No'. I am now hesitant to select Yes because I don't know what is best.

Since it's been years since my previous OS install I just don't remember how I set up everything at the time.

Can anyone tell me what the correct/preferred way is of installing/using libraries and what the deal is with the .vcxitems files?

From memory if I wanted to use a library, like the 'SHT31-0.5.0' one in Micro Explorer I would go to the Installed tab, search for that library and click it and a reference would be added to my solution. That however does nothing right now so maybe I don't remember this correctly.

Also to this day I still don't really understand what the IDE selection does. I have the option between 'Arduino 2' and 'Visual Micro (No IDE)'. Why is it called 'No IDE' as clearly I do have an IDE installed: VS2022 (and Arduino 2). Switching between the 2 options also seemingly makes no difference.

TL;DR : How do I get the .vcxitems files re-generated and if I shouldn't use them, then how do I use the libraries?

Thank you very much for the detailed answer.

I understand now why/when one would use shared libraries. One reason to have the shared projects that you didn't mention but which I find handy myself is that that way I can immediately see which version of a library my code is supposed to work with.

If say SHT31-0.5.0 is a shared project (and this visible as SHT31-0.5.0 in my solution explorer) then even after a complete re-install 2 years laters I immediately know that my code will work with SHT31-0.5.0 and might not work with the then latest version SHT31-x.y.z.

As a fix (for when not using shared projects) I have now added a versions.txt file to my code that lists the actual library versions it should be compiled against. If anyone knows of a better way I'd be happy to hear it.

A little update:

Since I am now no longer using shared projects my build times have gone down from something like 10 minutes to under a minute. 

It's now a lot of "Using previously compiled file: xyz.cpp.o

Choice! Very happy with this.