Upgrade Middleware sample to Net9

[OzBob]

Upgrade middleware sample to .Net9 and sets static and sync methods and classes to async compatible

@jviau
@kshyju

resolves #2920

Pull request checklist

• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• My changes do not need to be backported to a previous version
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• I have added all required tests (Unit tests, E2E tests)

[jviau]

Why does this sample need to be updated to net9? net8 is perfectly fine as far as I am concerned.

[OzBob]

Why does this sample need to be updated to net9? net8 is perfectly fine as far as I am concerned.

Thank you @jviau for your feedback, as a contributor I would hope you will consider the upcoming end of support for the in-process AzFn model and consider that this PR is just a ahead of it's time, since eventually all the samples will need upgrading, not just to .Net9(+) but into the isolated model, since:

“Support will end for the in-process model on November 10, 2026. We highly recommend that you migrate your apps to the isolated worker model for full support.”

[SeanFeldman]

Why does this sample need to be updated to net9? net8 is perfectly fine as far as I am concerned.

Thank you @jviau for your feedback, as a contributor I would hope you will consider the upcoming end of support for the in-process AzFn model and consider that this PR is just a ahead of it's time, since eventually all the samples will need upgrading, not just to .Net9(+) but into the isolated model, since:

“Support will end for the in-process model on November 10, 2026. We highly recommend that you migrate your apps to the isolated worker model for full support.”

There's a lot of confusion here.
First, this repository is not for the in-process SDK. This repository is for the isolated worker SDK. What you quoted is not applicable because it simply doesn't apply.

Next, what @jviau was saying is that .NET 8 is an LTS while .NET 9 is an STS. .NET 8 will be supported longer than .NET 9.

So given that .NET 9

• Will be out of the official support faster than .NET 8
• Won't bring any significant benefits to the samples
• Not an LTS

There's no value in changing samples from .NET 8.
The rest of your changes (async, ignored files, and package updates) are still valid.

Hope that clarifies it a bit.

[jviau]

Updating this sample to .NET9 is not desired. If you want to proceed with this PR, please revert to .NET8 and address the other review comments.

[jviau]

I would prefer gitignore changes in a separate PR.

[jviau]

please keep the previous indentation style for this file (2 spaces, not 4)

[microsoft-github-policy-service]

This pull request has been automatically marked as stale because it has been marked as requiring author feedback but has not had any activity for 7 days. It will be closed if no further activity occurs within 7 days of this comment.