Document the new performance counters about doc HOT 3 CLOSED

In the docs https://www.npgsql.org/doc/performance.html says "The feature was removed in Npgsql 5.0."

We are still using Full .Net Framework and version 5.0.1.1 of NpgSQL. I need to performance metrics to diagnose issues that occur under load. Is this possible and how can I do this?, If not possible, does it make sense to roll back or are the features coming soon?

from doc.

Npgsql 5.0 no longer targets .NET Framework - it's usable under .NET Framework because we target .NET Standard 2.0, but the Windows Performance Counter APIs are unavailable there. So it's not possible to continue supporting these, and they won't be coming back.

In .NET Core there's the new cross-platform performance counters (which are also considerably better) - but these aren't available under .NET Framework. I do need to document these for Npgsql (that's what this issue is about).

If you absolutely need counters, you'll have to either switch to .NET Core (which I hope you do at some point anyway), or downgrade back to Npgsql 4.1.

from doc.

We would love to move to .net core, but this is large legacy codebase and it isn't feasible at the moment. Reverting to the previous version of Npgsql sounds like our only option at the moment. Thanks for responding.

from doc.