This PR is targeting main, which is now for .NET 11-facing work. If you intended to target .NET 10, either retarget this PR to release/10.0.1xx or make sure you backport the change to release/10.0.1xx after merging. See #50394 for more details.

Thanks for your PR, @@wes-sleeman.
To learn about the PR process and branching schedule of this repo, please take a look at the SDK PR Guide.

@dotnet-policy-service agree

@dotnet/domestic-cat
I think this is ready for review and (hopefully) merge. Let me know if anything else needs to be done to get this ready.

@wes-sleeman All Watch stuff goes to @tmat, so we'll wait for him to chime in.

Thanks for making your contribution! We're technically still open for SDK-level changes for a couple more weeks, so it's possible this could make it to .NET 10. That would require a backport (which we can trigger) once this merges - since main is technically .NET 11 already!

It's very unlikely that we would backport this to 8.x or 9.x SDKs without a really compelling customer use case, or some kind of external partner to justify the work + ongoing maintenance. The SDK is mostly a fix-forward kind of component for features - majorly-impactful bug fixes and security updates are the main category of thing that would be backported.

@baronfel, thanks for the quick reply! Would enjoy this making it into .NET 10 as this has been a blocker for me leveraging .NET with my team at work (enough to make me file this PR in my spare time!), so happy to hear there's a chance on that.

@wes-sleeman Would you mind updating your PR to resovle the conflicts?

You'll need to add a new property to EnvironmentOptions flow it as a parameter to BrowserRefreshServer constructor.
I'd also prefer the type of this property to be int? (optional port), not string.

@tmat Sorry for the delay! Only just got around to resolving this. Looks like you re-architected this whole feature a few days ago. I've merged the changes in sensibly and added the necessary helper function to make it an int? as requested. Let me know if you run into any other trouble with it. :)

@wes-sleeman Thanks for your effort!

/backport to release/10.0.1xx

Started backporting to release/10.0.1xx: https://github.com/dotnet/sdk/actions/runs/17746309610

@tmat backporting to "release/10.0.1xx" failed, the patch most likely resulted in conflicts:

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patch

Applying: Added port selection logic to the browser refresh script
Using index info to reconstruct a base tree...
A	src/BuiltInTools/dotnet-watch/Browser/BrowserRefreshServer.cs
Falling back to patching base and 3-way merge...
CONFLICT (modify/delete): src/BuiltInTools/dotnet-watch/Browser/BrowserRefreshServer.cs deleted in HEAD and modified in Added port selection logic to the browser refresh script.  Version Added port selection logic to the browser refresh script of src/BuiltInTools/dotnet-watch/Browser/BrowserRefreshServer.cs left in tree.
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
Patch failed at 0001 Added port selection logic to the browser refresh script
Error: The process '/usr/bin/git' failed with exit code 128

Please backport manually!